Update usages of ItemsControl Items/ItemsSource.

- Use `ItemsSource` when appropriate
- When `Items` is appropriate, don't use the setter

samples/ControlCatalog/MainView.xaml

@@ -241,7 +241,7 @@
               </ComboBox.Items>
             </ComboBox>
             <ComboBox HorizontalAlignment="Stretch"
-                      Items="{Binding WindowStates}"
+                      ItemsSource="{Binding WindowStates}"
                       SelectedItem="{Binding WindowState}" />
           </StackPanel>
         </Flyout>

samples/ControlCatalog/Pages/CompositionPage.axaml.cs

@@ -32,7 +32,7 @@ public partial class CompositionPage : UserControl
     protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
     {
         base.OnAttachedToVisualTree(e);
-        this.Get<ItemsControl>("Items").Items = CreateColorItems();
+        this.Get<ItemsControl>("Items").ItemsSource = CreateColorItems();
 
     }
 

samples/ControlCatalog/Pages/ContextFlyoutPage.xaml

@@ -61,7 +61,7 @@
         <Border.Styles>
           <Style Selector="MenuFlyoutPresenter MenuItem" x:DataType="viewModels:MenuItemViewModel">
             <Setter Property="Header" Value="{Binding Header}"/>
-            <Setter Property="Items" Value="{Binding Items}"/>
+            <Setter Property="ItemsSource" Value="{Binding Items}"/>
             <Setter Property="Command" Value="{Binding Command}"/>
             <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
           </Style>

samples/ControlCatalog/Pages/ContextMenuPage.xaml

@@ -51,13 +51,13 @@
         <Border.Styles>
           <Style Selector="ContextMenu MenuItem" x:DataType="viewModels:MenuItemViewModel">
             <Setter Property="Header" Value="{Binding Header}"/>
-            <Setter Property="Items" Value="{Binding Items}"/>
+            <Setter Property="ItemsSource" Value="{Binding Items}"/>
             <Setter Property="Command" Value="{Binding Command}"/>
             <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
           </Style>
         </Border.Styles>
         <Border.ContextMenu>
-          <ContextMenu Items="{Binding MenuItems}" />
+          <ContextMenu ItemsSource="{Binding MenuItems}" />
         </Border.ContextMenu>
         <TextBlock Text="Dynamically Generated"/>
       </Border>

samples/ControlCatalog/Pages/CursorPage.xaml

@@ -8,7 +8,7 @@
       <TextBlock Classes="h2">Defines a cursor (mouse pointer)</TextBlock>
     </StackPanel>
 
-    <ListBox Grid.Row="1" Items="{Binding StandardCursors}" Margin="0 8 8 8">
+    <ListBox Grid.Row="1" ItemsSource="{Binding StandardCursors}" Margin="0 8 8 8">
       <ListBox.Styles>
         <Style Selector="ListBoxItem">
           <Setter Property="Cursor" Value="{Binding Cursor}" x:DataType="viewModels:StandardCursorModel"/>

samples/ControlCatalog/Pages/DialogsPage.xaml.cs

@@ -106,7 +106,7 @@ namespace ControlCatalog.Pages
                     Directory = initialDirectory,
                     InitialFileName = initialFileName
                 }.ShowAsync(GetWindow());
-                results.Items = result;
+                results.ItemsSource = result;
                 resultsVisible.IsVisible = result?.Any() == true;
             };
             this.Get<Button>("OpenMultipleFiles").Click += async delegate
@@ -118,7 +118,7 @@ namespace ControlCatalog.Pages
                     Directory = lastSelectedDirectory?.Path is {IsAbsoluteUri:true} path ? path.LocalPath : null,
                     AllowMultiple = true
                 }.ShowAsync(GetWindow());
-                results.Items = result;
+                results.ItemsSource = result;
                 resultsVisible.IsVisible = result?.Any() == true;
             };
             this.Get<Button>("SaveFile").Click += async delegate
@@ -132,7 +132,7 @@ namespace ControlCatalog.Pages
                     DefaultExtension = filters?.Any() == true ? "txt" : null,
                     InitialFileName = "test.txt"
                 }.ShowAsync(GetWindow());
-                results.Items = new[] { result };
+                results.ItemsSource = new[] { result };
                 resultsVisible.IsVisible = result != null;
             };
             this.Get<Button>("SelectFolder").Click += async delegate
@@ -149,7 +149,7 @@ namespace ControlCatalog.Pages
                 else
                 {
                     SetFolder(await GetStorageProvider().TryGetFolderFromPathAsync(result));
-                    results.Items = new[] { result };
+                    results.ItemsSource = new[] { result };
                     resultsVisible.IsVisible = true;
                 }
             };
@@ -164,7 +164,7 @@ namespace ControlCatalog.Pages
                 {
                     AllowDirectorySelection = true
                 });
-                results.Items = result;
+                results.ItemsSource = result;
                 resultsVisible.IsVisible = result?.Any() == true;
             };
             this.Get<Button>("DecoratedWindow").Click += delegate
@@ -332,7 +332,7 @@ namespace ControlCatalog.Pages
                     }
                 }
 
-                results.Items = mappedResults;
+                results.ItemsSource = mappedResults;
                 resultsVisible.IsVisible = mappedResults.Any();
             }
         }

samples/ControlCatalog/Pages/ListBoxPage.xaml

@@ -30,7 +30,7 @@
       <Button Command="{Binding RemoveItemCommand}">Remove</Button>
       <Button Command="{Binding SelectRandomItemCommand}">Select Random Item</Button>
     </StackPanel>
-    <ListBox Items="{Binding Items}"
+    <ListBox ItemsSource="{Binding Items}"
              Selection="{Binding Selection}"
              DisplayMemberBinding="{Binding (viewModels:ItemModel).ID, StringFormat='{}Item {0:N0}'}"
              AutoScrollToSelectedItem="{Binding AutoScrollToSelectedItem}"

samples/ControlCatalog/Pages/MenuPage.xaml

@@ -45,11 +45,11 @@
 
             <StackPanel>
                 <TextBlock Classes="h3" Margin="4 8">Dyanamically generated</TextBlock>
-                <Menu Items="{Binding MenuItems}">
+                <Menu ItemsSource="{Binding MenuItems}">
                     <Menu.Styles>
                         <Style Selector="MenuItem" x:DataType="viewModels:MenuItemViewModel">
                             <Setter Property="Header" Value="{Binding Header}"/>
-                            <Setter Property="Items" Value="{Binding Items}"/>
+                            <Setter Property="ItemsSource" Value="{Binding Items}"/>
                             <Setter Property="Command" Value="{Binding Command}"/>
                             <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
                         </Style>
@@ -68,7 +68,7 @@
                         <Separator/>
                         <MenuItem Header="Execu_te Script..." />
                         <Separator/>
-                        <MenuItem Header="_Recent" Items="{Binding RecentItems}">
+                        <MenuItem Header="_Recent" ItemsSource="{Binding RecentItems}">
                             <MenuItem.Styles>
                                 <Style Selector="MenuItem" x:DataType="viewModels:MenuItemViewModel">
                                     <Setter Property="Header" Value="{Binding Header}"/>

samples/ControlCatalog/Pages/NativeEmbedPage.xaml.cs

@@ -33,10 +33,10 @@ namespace ControlCatalog.Pages
         {
             new ContextMenu()
             {
-                Items = new List<MenuItem>
-            {
-                new MenuItem() { Header = "Test" }, new MenuItem() { Header = "Test" }
-            }
+                Items =
+                {
+                    new MenuItem() { Header = "Test" }, new MenuItem() { Header = "Test" }
+                }
             }.Open((Control)sender);
         }
 

samples/ControlCatalog/Pages/NumericUpDownPage.xaml

@@ -27,7 +27,7 @@
       </Grid>
       <Grid Grid.Row="0" Grid.Column="1" Margin="8" ColumnDefinitions="Auto, 120" RowDefinitions="Auto,Auto,Auto,Auto,Auto">
         <TextBlock Grid.Row="0" Grid.Column="0" VerticalAlignment="Center" Margin="2">FormatString:</TextBlock>
-        <ComboBox Grid.Row="0" Grid.Column="1" Items="{Binding Formats}" SelectedItem="{Binding SelectedFormat}"
+        <ComboBox Grid.Row="0" Grid.Column="1" ItemsSource="{Binding Formats}" SelectedItem="{Binding SelectedFormat}"
                   VerticalAlignment="Center" Margin="2">
           <ComboBox.ItemTemplate>
             <DataTemplate>
@@ -41,11 +41,11 @@
         </ComboBox>
 
         <TextBlock Grid.Row="1" Grid.Column="0" VerticalAlignment="Center" Margin="2">ButtonSpinnerLocation:</TextBlock>
-        <ComboBox Grid.Row="1" Grid.Column="1" Items="{Binding SpinnerLocations}" SelectedItem="{Binding #upDown.ButtonSpinnerLocation}"
+        <ComboBox Grid.Row="1" Grid.Column="1" ItemsSource="{Binding SpinnerLocations}" SelectedItem="{Binding #upDown.ButtonSpinnerLocation}"
                   VerticalAlignment="Center" Margin="2"/>
 
         <TextBlock Grid.Row="2" Grid.Column="0" VerticalAlignment="Center" Margin="2">CultureInfo:</TextBlock>
-        <ComboBox x:Name="CultureSelector" Grid.Row="2" Grid.Column="1" Items="{Binding Cultures}"
+        <ComboBox x:Name="CultureSelector" Grid.Row="2" Grid.Column="1" ItemsSource="{Binding Cultures}"
                   VerticalAlignment="Center" Margin="2"/>
 
         <TextBlock Grid.Row="3" Grid.Column="0" VerticalAlignment="Center" Margin="2">Watermark:</TextBlock>

samples/ControlCatalog/Pages/RefreshContainerPage.axaml

@@ -21,7 +21,7 @@
                       Margin="5">
       <ListBox HorizontalAlignment="Stretch"
                VerticalAlignment="Top"
-               Items="{Binding Items}"/>
+               ItemsSource="{Binding Items}"/>
     </RefreshContainer>
   </DockPanel>
 </UserControl>

samples/ControlCatalog/Pages/ScrollSnapPage.xaml

@@ -16,14 +16,14 @@
         <StackPanel Orientation="Vertical"
                     Spacing="4">
           <TextBlock Text="Snap Point Type" />
-          <ComboBox Items="{Binding AvailableSnapPointsType}"
+          <ComboBox ItemsSource="{Binding AvailableSnapPointsType}"
                     SelectedItem="{Binding SnapPointsType}" />
         </StackPanel>
 
         <StackPanel Orientation="Vertical"
                     Spacing="4">
           <TextBlock Text="Snap Point Alignment" />
-          <ComboBox Items="{Binding AvailableSnapPointsAlignment}"
+          <ComboBox ItemsSource="{Binding AvailableSnapPointsAlignment}"
                     SelectedItem="{Binding SnapPointsAlignment}" />
         </StackPanel>
 

samples/ControlCatalog/Pages/ScrollViewerPage.xaml

@@ -13,12 +13,12 @@
 
         <StackPanel Orientation="Vertical" Spacing="4">
           <TextBlock Text="Horizontal Scroll" />
-          <ComboBox Items="{Binding AvailableVisibility}" SelectedItem="{Binding HorizontalScrollVisibility}" />
+          <ComboBox ItemsSource="{Binding AvailableVisibility}" SelectedItem="{Binding HorizontalScrollVisibility}" />
         </StackPanel>
 
         <StackPanel Orientation="Vertical" Spacing="4">
           <TextBlock Text="Vertical Scroll" />
-          <ComboBox Items="{Binding AvailableVisibility}" SelectedItem="{Binding VerticalScrollVisibility}" />
+          <ComboBox ItemsSource="{Binding AvailableVisibility}" SelectedItem="{Binding VerticalScrollVisibility}" />
         </StackPanel>
       </StackPanel>
 

samples/ControlCatalog/Pages/TabStripPage.xaml

@@ -18,7 +18,7 @@
         <Separator Margin="0 16"/>
 
         <TextBlock Classes="h1">Dynamically generated</TextBlock>
-        <TabStrip Items="{Binding Tabs}">
+        <TabStrip ItemsSource="{Binding Tabs}">
             <TabStrip.Styles>
                 <Style Selector="TabStripItem" x:DataType="viewModels:TabControlPageViewModelItem">
                     <Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>

samples/ControlCatalog/Pages/ThemePage.axaml.cs

@@ -12,7 +12,7 @@ namespace ControlCatalog.Pages
         {
             InitializeComponent();
 
-            Selector.Items = new[]
+            Selector.ItemsSource = new[]
             {
                 ThemeVariant.Default,
                 ThemeVariant.Dark,

samples/ControlCatalog/Pages/TransitioningContentControlPage.axaml

@@ -53,7 +53,7 @@
             
             <StackPanel Margin="5" Spacing="5" Grid.IsSharedSizeScope="True">
                 <HeaderedContentControl Header="Select a transition">
-                     <ComboBox Items="{Binding PageTransitions}" SelectedItem="{Binding SelectedTransition}" />
+                     <ComboBox ItemsSource="{Binding PageTransitions}" SelectedItem="{Binding SelectedTransition}" />
                 </HeaderedContentControl>
                 <HeaderedContentControl Header="Duration">
                      <NumericUpDown Value="{Binding Duration}" Increment="250" Minimum="100" />

samples/ControlCatalog/Pages/TreeViewPage.xaml

@@ -11,7 +11,7 @@
                 HorizontalAlignment="Center"
                 Spacing="16">
       <StackPanel Orientation="Vertical" Spacing="8">
-        <TreeView Items="{Binding Items}" SelectedItems="{Binding SelectedItems}" SelectionMode="{Binding SelectionMode}" Width="250" Height="350">
+        <TreeView ItemsSource="{Binding Items}" SelectedItems="{Binding SelectedItems}" SelectionMode="{Binding SelectionMode}" Width="250" Height="350">
           <TreeView.ItemTemplate>
             <TreeDataTemplate ItemsSource="{Binding Children}">
               <TextBlock Text="{Binding Header}"/>

samples/IntegrationTestApp/MainWindow.axaml

@@ -109,7 +109,7 @@
           <StackPanel DockPanel.Dock="Bottom">
             <Button Name="ListBoxSelectionClear">Clear Selection</Button>
           </StackPanel>
-          <ListBox Name="BasicListBox" Items="{Binding ListBoxItems}" SelectionMode="Multiple"/>
+          <ListBox Name="BasicListBox" ItemsSource="{Binding ListBoxItems}" SelectionMode="Multiple"/>
         </DockPanel>
       </TabItem>
       

src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorPicker.xaml

@@ -165,7 +165,7 @@
                     </TabItem.Header>
                     <ListBox Theme="{StaticResource ColorViewPaletteListBoxTheme}"
                              ItemContainerTheme="{StaticResource ColorViewPaletteListBoxItemTheme}"
-                             Items="{TemplateBinding PaletteColors}"
+                             ItemsSource="{TemplateBinding PaletteColors}"
                              SelectedItem="{Binding Color, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource DoNothingForNullConverter}, Mode=TwoWay}"
                              UseLayoutRounding="False"
                              Margin="12">

src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml

@@ -414,7 +414,7 @@
               </TabItem.Header>
               <ListBox Theme="{StaticResource ColorViewPaletteListBoxTheme}"
                        ItemContainerTheme="{StaticResource ColorViewPaletteListBoxItemTheme}"
-                       Items="{TemplateBinding PaletteColors}"
+                       ItemsSource="{TemplateBinding PaletteColors}"
                        SelectedItem="{Binding Color, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource DoNothingForNullConverter}, Mode=TwoWay}"
                        UseLayoutRounding="False"
                        Margin="12">

src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorPicker.xaml

@@ -165,7 +165,7 @@
                     </TabItem.Header>
                     <ListBox Theme="{StaticResource ColorViewPaletteListBoxTheme}"
                              ItemContainerTheme="{StaticResource ColorViewPaletteListBoxItemTheme}"
-                             Items="{TemplateBinding PaletteColors}"
+                             ItemsSource="{TemplateBinding PaletteColors}"
                              SelectedItem="{Binding Color, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource DoNothingForNullConverter}, Mode=TwoWay}"
                              UseLayoutRounding="False"
                              Margin="12">

src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml

@@ -376,7 +376,7 @@
               </TabItem.Header>
               <ListBox Theme="{StaticResource ColorViewPaletteListBoxTheme}"
                        ItemContainerTheme="{StaticResource ColorViewPaletteListBoxItemTheme}"
-                       Items="{TemplateBinding PaletteColors}"
+                       ItemsSource="{TemplateBinding PaletteColors}"
                        SelectedItem="{Binding Color, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource DoNothingForNullConverter}, Mode=TwoWay}"
                        UseLayoutRounding="False"
                        Margin="12">

src/Avalonia.Controls/ItemsControl.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Automation.Peers;
 using Avalonia.Collections;
 using Avalonia.Controls.Generators;

src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml

@@ -40,7 +40,7 @@
              BorderBrush="{DynamicResource ThemeControlMidBrush}"
              BorderThickness="0,0,0,1"
              FontFamily="/Assets/Fonts/SourceSansPro-Regular.ttf"
-             Items="{Binding History}">
+             ItemsSource="{Binding History}">
       <ListBox.ItemTemplate>
         <DataTemplate>
           <StackPanel Orientation="Vertical">

src/Avalonia.Diagnostics/Diagnostics/Views/ControlDetailsView.xaml

@@ -124,7 +124,7 @@
         </Grid>
 
         <ScrollViewer Grid.Row="1" HorizontalScrollBarVisibility="Disabled">
-          <ItemsControl Items="{Binding AppliedStyles}" >
+          <ItemsControl ItemsSource="{Binding AppliedStyles}" >
             <ItemsControl.ItemTemplate>
               <DataTemplate>
                 <Border BorderThickness="0,0,0,1" BorderBrush="#6C6C6C" Opacity="{Binding IsActive, Converter={StaticResource BoolToOpacity}}">
@@ -142,7 +142,7 @@
                       <TextBlock Grid.Row="0" Text="{Binding Name}" />
                     </Expander.Header>
 
-                    <ItemsControl Margin="20,0,0,0" Grid.Row="1" Items="{Binding Setters}">
+                    <ItemsControl Margin="20,0,0,0" Grid.Row="1" ItemsSource="{Binding Setters}">
                       
                       <ItemsControl.Styles>
                         <Style Selector="TextBlock.property-name">
@@ -253,7 +253,7 @@
         </ScrollViewer>
 
         <Expander Header="Pseudo Classes" Grid.Row="2">
-          <ItemsControl Items="{Binding PseudoClasses}">
+          <ItemsControl ItemsSource="{Binding PseudoClasses}">
             <ItemsControl.ItemsPanel>
               <ItemsPanelTemplate>
                 <WrapPanel />

src/Avalonia.Diagnostics/Diagnostics/Views/EventsPageView.xaml

@@ -45,7 +45,7 @@
                               UseWholeWordFilter="{Binding UseWholeWordFilter}"
                               UseRegexFilter="{Binding UseRegexFilter}" />
 
-      <TreeView Grid.Row="1" Items="{Binding Nodes}" SelectedItem="{Binding SelectedNode, Mode=TwoWay}" >
+      <TreeView Grid.Row="1" ItemsSource="{Binding Nodes}" SelectedItem="{Binding SelectedNode, Mode=TwoWay}" >
         <TreeView.DataTemplates>
           <TreeDataTemplate DataType="vm:EventTreeNodeBase"
                             ItemsSource="{Binding Children}">
@@ -71,7 +71,7 @@
 
     <Grid RowDefinitions="*,4,2*,Auto" Grid.Column="2">
 
-      <ListBox Name="EventsList" Items="{Binding RecordedEvents}"
+      <ListBox Name="EventsList" ItemsSource="{Binding RecordedEvents}"
                SelectedItem="{Binding SelectedEvent, Mode=TwoWay}">
 
         <ListBox.ItemTemplate>
@@ -108,7 +108,7 @@
       <DockPanel Grid.Row="2" LastChildFill="True">
         <TextBlock DockPanel.Dock="Top" FontSize="16" Text="Event chain:" />
 
-        <ListBox Items="{Binding SelectedEvent.EventChain}">
+        <ListBox ItemsSource="{Binding SelectedEvent.EventChain}">
           <ListBox.ItemTemplate>
             <DataTemplate>
               <ListBoxItem Classes.handled="{Binding Handled}">

src/Avalonia.Diagnostics/Diagnostics/Views/PropertyValueEditorView.cs

@@ -221,7 +221,7 @@ namespace Avalonia.Diagnostics.Views
                 return CreateControl<ComboBox>(
                     SelectingItemsControl.SelectedItemProperty, init: c =>
                     {
-                        c.Items = Enum.GetValues(propertyType);
+                        c.ItemsSource = Enum.GetValues(propertyType);
                     });
 
             var tb = CreateControl<CommitTextBox>(

src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml

@@ -6,7 +6,7 @@
   <Grid ColumnDefinitions="0.35*,4,0.65*">
     <TreeView Name="tree"
               BorderThickness="0"
-              Items="{Binding Nodes}"
+              ItemsSource="{Binding Nodes}"
               SelectedItem="{Binding SelectedNode, Mode=TwoWay}">
       <TreeView.DataTemplates>
         <TreeDataTemplate DataType="vm:TreeNode"

src/Avalonia.Themes.Fluent/Controls/DataValidationErrors.xaml

@@ -50,7 +50,7 @@
       <DataTemplate>
         <ItemsControl x:DataType="DataValidationErrors"
                       Foreground="{DynamicResource SystemControlErrorTextForegroundBrush}"
-                      Items="{Binding}">
+                      ItemsSource="{Binding}">
           <ItemsControl.Styles>
             <Style Selector="TextBlock">
               <Setter Property="TextWrapping" Value="Wrap" />
@@ -98,7 +98,7 @@
             </Style>
           </Panel.Styles>
           <ToolTip.Tip>
-            <ItemsControl Items="{Binding}" x:DataType="collections:IEnumerable" />
+            <ItemsControl ItemsSource="{Binding}" x:DataType="collections:IEnumerable" />
           </ToolTip.Tip>
           <Path Width="14"
                 Height="14"

src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml

@@ -136,7 +136,7 @@
             x:DataType="internal:ManagedFileChooserViewModel">
       <ControlTemplate>
         <DockPanel>
-          <ListBox x:Name="PART_QuickLinks" DockPanel.Dock="Left" Items="{Binding QuickLinks}" SelectedIndex="{Binding QuickLinksSelectedIndex}" Focusable="False">
+          <ListBox x:Name="PART_QuickLinks" DockPanel.Dock="Left" ItemsSource="{Binding QuickLinks}" SelectedIndex="{Binding QuickLinksSelectedIndex}" Focusable="False">
             <ListBox.ItemTemplate>
               <DataTemplate>
                 <StackPanel Spacing="4" Orientation="Horizontal" Background="Transparent">
@@ -173,7 +173,7 @@
               <DockPanel DockPanel.Dock="Top" Margin="0,0,0,4">
                 <ComboBox DockPanel.Dock="Right"
                     IsVisible="{Binding ShowFilters}"
-                    Items="{Binding Filters}"
+                    ItemsSource="{Binding Filters}"
                     SelectedItem="{Binding SelectedFilter}" />
                 <TextBox Text="{Binding FileName}" Watermark="File name" IsVisible="{Binding !SelectingFolder}" />
               </DockPanel>
@@ -220,7 +220,7 @@
               <TextBlock Grid.Column="8" Text="Size" />
             </Grid>
             <ListBox x:Name="PART_Files"
-                Items="{Binding Items}"
+                ItemsSource="{Binding Items}"
                 Margin="0 5"
                 SelectionMode="{Binding SelectionMode}"
                 SelectedItems="{Binding SelectedItems}"

src/Avalonia.Themes.Fluent/Controls/NativeMenuBar.xaml

@@ -7,13 +7,13 @@
       <ControlTemplate>
         <Menu
           IsVisible="{Binding !$parent[TopLevel].(NativeMenu.IsNativeMenuExported)}"
-          Items="{Binding $parent[TopLevel].(NativeMenu.Menu).Items}">
+          ItemsSource="{Binding $parent[TopLevel].(NativeMenu.Menu).Items}">
           <Menu.Styles>
             <Style Selector="MenuItem" x:DataType="NativeMenuItem">
               <Setter Property="Header" Value="{Binding Header}"/>
               <Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>
               <Setter Property="InputGesture" Value="{Binding Gesture}"/>
-              <Setter Property="Items" Value="{Binding Menu.Items}"/>
+              <Setter Property="ItemsSource" Value="{Binding Menu.Items}"/>
               <Setter Property="Command" Value="{Binding Command}"/>
               <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
               <Setter Property="(NativeMenuBar.EnableMenuItemClickForwarding)" Value="True"/>

src/Avalonia.Themes.Simple/Controls/DataValidationErrors.xaml

@@ -35,7 +35,7 @@
           </Canvas.Styles>
           <ToolTip.Tip>
             <ItemsControl x:DataType="DataValidationErrors"
-                          Items="{Binding}" />
+                          ItemsSource="{Binding}" />
           </ToolTip.Tip>
           <Path Data="M14,7 A7,7 0 0,0 0,7 M0,7 A7,7 0 1,0 14,7 M7,3l0,5 M7,9l0,2"
                 Stroke="{DynamicResource ErrorBrush}"

src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml

@@ -101,7 +101,7 @@
           <ComboBox Margin="0,5,0,0"
                     DockPanel.Dock="Bottom"
                     IsVisible="{Binding ShowFilters}"
-                    Items="{Binding Filters}"
+                    ItemsSource="{Binding Filters}"
                     SelectedItem="{Binding SelectedFilter}" />
 
           <TextBox DockPanel.Dock="Bottom"
@@ -114,7 +114,7 @@
                    BorderBrush="Transparent"
                    DockPanel.Dock="Left"
                    Focusable="False"
-                   Items="{Binding QuickLinks}"
+                   ItemsSource="{Binding QuickLinks}"
                    SelectedIndex="{Binding QuickLinksSelectedIndex}">
             <ListBox.ItemTemplate>
               <DataTemplate>
@@ -160,7 +160,7 @@
             </Grid>
             <ListBox x:Name="PART_Files"
                      Margin="0,5"
-                     Items="{Binding Items}"
+                     ItemsSource="{Binding Items}"
                      ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                      SelectedItems="{Binding SelectedItems}"
                      SelectionMode="{Binding SelectionMode}">

src/Avalonia.Themes.Simple/Controls/NativeMenuBar.xaml

@@ -7,13 +7,13 @@
     <Setter Property="Template">
       <ControlTemplate>
         <Menu IsVisible="{Binding !$parent[TopLevel].(NativeMenu.IsNativeMenuExported)}"
-              Items="{Binding $parent[TopLevel].(NativeMenu.Menu).Items}">
+              ItemsSource="{Binding $parent[TopLevel].(NativeMenu.Menu).Items}">
           <Menu.Styles>
             <Style Selector="MenuItem" x:DataType="NativeMenuItem">
               <Setter Property="Header" Value="{Binding Header}"/>
               <Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>
               <Setter Property="InputGesture" Value="{Binding Gesture}"/>
-              <Setter Property="Items" Value="{Binding Menu.Items}"/>
+              <Setter Property="ItemsSource" Value="{Binding Menu.Items}"/>
               <Setter Property="Command" Value="{Binding Command}"/>
               <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
               <Setter Property="(NativeMenuBar.EnableMenuItemClickForwarding)" Value="True"/>

src/Windows/Avalonia.Win32/TrayIconImpl.cs

@@ -150,7 +150,7 @@ namespace Avalonia.Win32
                 TransparencyLevelHint = WindowTransparencyLevel.Transparent,
                 Content = new TrayIconMenuFlyoutPresenter()
                 {
-                    Items = menuItems
+                    ItemsSource = menuItems
                 }
             };
 

src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Win32
 
                     if (item.Menu != null)
                     {
-                        newItem.Items = Populate(item.Menu);
+                        newItem.ItemsSource = Populate(item.Menu);
                     }
                     else if (item.HasClickHandlers && item is INativeMenuItemExporterEventsImplBridge bridge)
                     {

tests/Avalonia.Controls.UnitTests/CarouselTests.cs

@@ -23,7 +23,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = new[]
+                ItemsSource = new[]
                 {
                     "Foo",
                     "Bar"
@@ -43,7 +43,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = new[]
+                ItemsSource = new[]
                 {
                     "Foo",
                     "Bar"
@@ -73,7 +73,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             Prepare(target);
@@ -88,7 +88,7 @@ namespace Avalonia.Controls.UnitTests
             newItems.RemoveAt(0);
             Layout(target);
 
-            target.Items = newItems;
+            target.ItemsSource = newItems;
             Layout(target);
 
             child = GetContainerTextBlock(target.GetRealizedContainers().Single());
@@ -104,7 +104,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             Prepare(target);
@@ -133,7 +133,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             Prepare(target);
@@ -144,7 +144,7 @@ namespace Avalonia.Controls.UnitTests
 
             Assert.Equal("Foo", child.Text);
 
-            target.Items = null;
+            target.ItemsSource = null;
             Layout(target);
 
             var numChildren = target.GetRealizedContainers().Count();
@@ -166,7 +166,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 2
             };
 
@@ -193,7 +193,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             Prepare(target);
@@ -225,7 +225,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new Carousel
             {
                 Template = CarouselTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             Prepare(target);

tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs

@@ -23,7 +23,7 @@ namespace Avalonia.Controls.UnitTests
         {
             var target = new ComboBox
             {
-                Items = new[] { "Foo", "Bar" },
+                ItemsSource = new[] { "Foo", "Bar" },
             };
 
             _helper.Down(target);
@@ -43,7 +43,7 @@ namespace Avalonia.Controls.UnitTests
         {
             var target = new ComboBox
             {
-                Items = new[] { "Foo", "Bar" },
+                ItemsSource = new[] { "Foo", "Bar" },
             };
 
             _helper.Down(target);
@@ -66,15 +66,14 @@ namespace Avalonia.Controls.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.RealFocus))
             {
-                var items = new[]
-                {
-                    new ComboBoxItem() { Content = "bla" },
-                    new ComboBoxItem() { Content = "dd" },
-                    new ComboBoxItem() { Content = "sdf", IsEnabled = false }
-                };
                 var target = new ComboBox
                 {
-                    Items = items,
+                    Items =
+                    {
+                        new ComboBoxItem() { Content = "bla" },
+                        new ComboBoxItem() { Content = "dd" },
+                        new ComboBoxItem() { Content = "sdf", IsEnabled = false }
+                    },
                     Template = GetTemplate(),
                     WrapSelection = true
                 };
@@ -104,15 +103,14 @@ namespace Avalonia.Controls.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.RealFocus))
             {
-                var items = new[]
-                {
-                    new ComboBoxItem() { Content = "bla" },
-                    new ComboBoxItem() { Content = "dd", IsEnabled = false },
-                    new ComboBoxItem() { Content = "sdf" }
-                };
                 var target = new ComboBox
                 {
-                    Items = items,
+                    Items =
+                    {
+                        new ComboBoxItem() { Content = "bla" },
+                        new ComboBoxItem() { Content = "dd", IsEnabled = false },
+                        new ComboBoxItem() { Content = "sdf" }
+                    },
                     Template = GetTemplate()
                 };
                 var root = new TestRoot(target);
@@ -139,10 +137,9 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void SelectionBoxItem_Is_Rectangle_With_VisualBrush_When_Selection_Is_Control()
         {
-            var items = new[] { new Canvas() };
             var target = new ComboBox
             {
-                Items = items,
+                Items = { new Canvas() },
                 SelectedIndex = 0,
             };
             var root = new TestRoot(target);
@@ -152,7 +149,7 @@ namespace Avalonia.Controls.UnitTests
 
             var brush = rectangle.Fill as VisualBrush;
             Assert.NotNull(brush);
-            Assert.Same(items[0], brush.Visual);
+            Assert.Same(target.Items[0], brush.Visual);
         }
 
         [Fact]
@@ -160,7 +157,7 @@ namespace Avalonia.Controls.UnitTests
         {
             var target = new ComboBox
             {
-                Items = new[] { new Canvas() },
+                Items = { new Canvas() },
                 SelectedIndex = 0,
                 Template = GetTemplate(),
             };
@@ -218,7 +215,7 @@ namespace Avalonia.Controls.UnitTests
             {
                 var target = new ComboBox
                 {
-                    Items = new[] { new Canvas() },
+                    Items = { new Canvas() },
                     SelectedIndex = 0,
                     Template = GetTemplate(),
                 };
@@ -257,7 +254,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ComboBox
                 {
                     Template = GetTemplate(),                    
-                    Items = items.Select(x => new ComboBoxItem { Content = x }).ToList(),
+                    ItemsSource = items.Select(x => new ComboBoxItem { Content = x })
                 };
 
                 target.ApplyTemplate();
@@ -326,7 +323,7 @@ namespace Avalonia.Controls.UnitTests
 
                 var target = new ComboBox
                 {
-                    Items = new[] { new Canvas() },
+                    Items = { new Canvas() },
                     SelectedIndex = 0,
                     Template = GetTemplate(),
                 };
@@ -363,17 +360,16 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void FlowDirection_Of_RectangleContent_Shuold_Be_LeftToRight()
         {
-            var items = new[]
-            {
-                new ComboBoxItem()
-                { 
-                    Content = new Control()
-                }
-            };
             var target = new ComboBox
             {
                 FlowDirection = FlowDirection.RightToLeft,
-                Items = items,
+                Items =
+                {
+                    new ComboBoxItem()
+                    {
+                        Content = new Control()
+                    }
+                },
                 Template = GetTemplate()
             };
 
@@ -393,16 +389,15 @@ namespace Avalonia.Controls.UnitTests
             {
                 Child = new Control()
             };
-            var items = new[]
-            { 
-                new ComboBoxItem()
-                {
-                    Content = parentContent.Child
-                }
-            };
             var target = new ComboBox
             {
-                Items = items,
+                Items = 
+                {
+                    new ComboBoxItem()
+                    {
+                        Content = parentContent.Child
+                    }
+                },
                 Template = GetTemplate()
             };
 
@@ -428,17 +423,16 @@ namespace Avalonia.Controls.UnitTests
                 {
                     Child = new Control()
                 };
-                var items = new[]
-                { 
-                    new ComboBoxItem()
-                    {
-                        Content = parentContent.Child
-                    }
-                };
                 var target = new ComboBox
                 {
                     FlowDirection = FlowDirection.RightToLeft,
-                    Items = items,
+                    Items =
+                    {
+                        new ComboBoxItem()
+                        {
+                            Content = parentContent.Child
+                        }
+                    },
                     Template = GetTemplate()
                 };
 

tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs

@@ -65,7 +65,7 @@ namespace Avalonia.Controls.UnitTests
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
             };
 
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -84,7 +84,7 @@ namespace Avalonia.Controls.UnitTests
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
             };
 
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -106,7 +106,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl();
 
             target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -119,7 +119,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl();
 
             target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter!.ApplyTemplate();
 
@@ -132,7 +132,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl();
 
             target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -151,7 +151,7 @@ namespace Avalonia.Controls.UnitTests
             };
 
             target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -174,7 +174,7 @@ namespace Avalonia.Controls.UnitTests
                 target.TemplatedParent = templatedParent;
                 target.Template = GetTemplate();
 
-                target.Items = new[] { "Foo" };
+                target.ItemsSource = new[] { "Foo" };
 
                 root.ApplyTemplate();
                 target.ApplyTemplate();
@@ -211,7 +211,7 @@ namespace Avalonia.Controls.UnitTests
             var child = new Control();
 
             target.Template = GetTemplate();
-            target.Items = new[] { child };
+            target.Items.Add(child);
             root.LayoutManager.ExecuteInitialLayoutPass();
 
             Assert.Equal(target, child.Parent);
@@ -228,7 +228,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             var root = new TestRoot(true, target);
@@ -314,9 +314,9 @@ namespace Avalonia.Controls.UnitTests
             var child = new Control();
 
             target.Template = GetTemplate();
-            target.Items = new[] { child };
+            target.Items.Add(child);
             target.ApplyTemplate();
-            target.Items = null;
+            target.Items.Clear();
 
             Assert.Null(child.Parent);
             Assert.Null(((ILogical)child).LogicalParent);
@@ -343,10 +343,9 @@ namespace Avalonia.Controls.UnitTests
         public void Adding_String_Item_Should_Make_ContentPresenter_Appear_In_LogicalChildren()
         {
             var target = new ItemsControl();
-            var child = new Control();
 
             target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -355,25 +354,6 @@ namespace Avalonia.Controls.UnitTests
             Assert.IsType<ContentPresenter>(logical.LogicalChildren[0]);
         }
 
-        [Fact]
-        public void Setting_Items_To_Null_Should_Remove_LogicalChildren()
-        {
-            var target = new ItemsControl();
-            var child = new Control();
-
-            target.Template = GetTemplate();
-            target.Items = new[] { "Foo" };
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
-
-            Assert.NotEmpty(target.GetLogicalChildren());
-
-            target.Items = null;
-
-            Assert.Equal(new ILogical[0], target.GetLogicalChildren());
-        }
-
-
         [Fact]
         public void Adding_Items_Should_Fire_LogicalChildren_CollectionChanged()
         {
@@ -393,7 +373,7 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Setting_Items_To_Null_Should_Fire_LogicalChildren_CollectionChanged()
+        public void Clearing_Items_Should_Fire_LogicalChildren_CollectionChanged()
         {
             var target = new ItemsControl();
             var child = new Control();
@@ -406,25 +386,7 @@ namespace Avalonia.Controls.UnitTests
             ((ILogical)target).LogicalChildren.CollectionChanged += (s, e) =>
                 called = e.Action == NotifyCollectionChangedAction.Remove;
 
-            target.Items = null;
-
-            Assert.True(called);
-        }
-
-        [Fact]
-        public void Changing_Items_Should_Fire_LogicalChildren_CollectionChanged()
-        {
-            var target = new ItemsControl();
-            var child = new Control();
-            var called = false;
-
-            target.Template = GetTemplate();
-            target.Items.Add(child);
-            target.ApplyTemplate();
-
-            ((ILogical)target).LogicalChildren.CollectionChanged += (s, e) => called = true;
-
-            target.Items = new[] { "Foo" };
+            target.Items.Clear();
 
             Assert.True(called);
         }
@@ -437,16 +399,13 @@ namespace Avalonia.Controls.UnitTests
             var called = false;
 
             target.Template = GetTemplate();
-            target.Items = items;
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            target.ItemsSource = items;
 
-            ((ILogical)target).LogicalChildren.CollectionChanged += (s, e) =>
-                called = e.Action == NotifyCollectionChangedAction.Remove;
+            ((ILogical)target).LogicalChildren.CollectionChanged += (s, e) => called = true;
 
             items.Remove("Bar");
 
-            Assert.True(called);
+            Assert.False(called);
         }
 
         [Fact]
@@ -474,7 +433,7 @@ namespace Avalonia.Controls.UnitTests
         {
             var target = new ItemsControl
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = GetTemplate(),
             };
 
@@ -507,7 +466,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = new[] { 1, 2, 3 },
+                ItemsSource = new[] { 1, 2, 3 },
             };
 
             Assert.DoesNotContain(":empty", target.Classes);
@@ -530,10 +489,10 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = new[] { 1, 2, 3 },
+                ItemsSource = new[] { 1, 2, 3 },
             };
 
-            target.Items = new int[0];
+            target.ItemsSource = new int[0];
 
             Assert.Contains(":empty", target.Classes);
         }
@@ -544,7 +503,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = new[] { 1, 2, 3 },
+                ItemsSource = new[] { 1, 2, 3 },
             };
 
             Assert.Equal(3, target.ItemCount);
@@ -558,7 +517,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Add(4);
@@ -578,7 +537,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Clear();
@@ -594,7 +553,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Add(1);
@@ -603,14 +562,14 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Single_Item_Class_Should_Be_Set_When_Items_Collection_Count_Increases_To_One()
+        public void Single_Item_Class_Should_Be_Set_When_ItemsSource_Collection_Count_Increases_To_One()
         {
             var items = new ObservableCollection<int>() { };
 
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Add(1);
@@ -626,7 +585,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Clear();
@@ -642,7 +601,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl()
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             items.Add(2);
@@ -669,7 +628,7 @@ namespace Avalonia.Controls.UnitTests
                 {
                     new FuncDataTemplate<Item>((x, __) => new Button { Content = x })
                 },
-                Items = items,
+                ItemsSource = items,
             };
 
             target.ApplyTemplate();
@@ -697,7 +656,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl
             {
                 Template = GetTemplate(),
-                Items = items,
+                ItemsSource = items,
             };
 
             target.ApplyTemplate();
@@ -721,7 +680,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ItemsControl
                 {
                     Template = GetTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                 };
 
                 var root = new TestRoot { Child = target };
@@ -757,7 +716,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ItemsControl
                 {
                     Template = GetTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                 };
 
                 var root = new TestRoot { Child = target };
@@ -785,7 +744,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ItemsControl
             {
                 Template = GetTemplate(),
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
             };
 
@@ -811,7 +770,7 @@ namespace Avalonia.Controls.UnitTests
                 DisplayMemberBinding = new Binding("Length")
             };
 
-            target.Items = new[] { "Foo" };
+            target.ItemsSource = new[] { "Foo" };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
@@ -830,7 +789,7 @@ namespace Avalonia.Controls.UnitTests
                 DisplayMemberBinding = new Binding("Value")
             };
 
-            target.Items = new[] { new Item("Foo", "Bar") };
+            target.ItemsSource = new[] { new Item("Foo", "Bar") };
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 

tests/Avalonia.Controls.UnitTests/ListBoxTests.cs

@@ -29,7 +29,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = ListBoxTemplate(),
-                Items = new[] { "Foo" },
+                ItemsSource = new[] { "Foo" },
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
             };
 
@@ -81,7 +81,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                 };
 
                 Prepare(target);
@@ -107,7 +107,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     ItemContainerTheme = theme,
                 };
 
@@ -124,12 +124,11 @@ namespace Avalonia.Controls.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
             {
-                var items = new[] { "Foo", "Bar", "Baz " };
                 var theme = new ControlTheme(typeof(ListBoxItem));
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = new[] { new ListBoxItem() },
+                    Items = { new ListBoxItem() },
                     ItemContainerTheme = theme,
                 };
 
@@ -149,7 +148,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 };
 
                 Prepare(target);
@@ -184,7 +183,7 @@ namespace Avalonia.Controls.UnitTests
                     {
                         new FuncDataTemplate<Item>((x, _) => new Button { Content = x })
                     },
-                    Items = items,
+                    ItemsSource = items,
                 };
 
                 Prepare(target);
@@ -208,7 +207,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList(),
+                    ItemsSource = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList(),
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
                     SelectedIndex = 0,
                 };
@@ -236,7 +235,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList(),
+                    ItemsSource = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList(),
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectedIndex = 0,
                 };
@@ -258,7 +257,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectedIndex = 0,
                 };
@@ -272,7 +271,7 @@ namespace Avalonia.Controls.UnitTests
                 items.Remove("Item 2");
                 Layout(target);
 
-                var actual = target.Presenter.Panel.Children.Cast<ListBoxItem>().Select(x => (string)x.Content).ToList();
+                var actual = target.GetRealizedContainers().Cast<ListBoxItem>().Select(x => (string)x.Content).ToList();
                 Assert.Equal(items.OrderBy(x => x), actual.OrderBy(x => x));
             }
         }
@@ -286,7 +285,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     SelectionMode = SelectionMode.Toggle,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 })
                 };
@@ -318,7 +317,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 })
                 };
 
@@ -364,7 +363,7 @@ namespace Avalonia.Controls.UnitTests
 
                 lm.ExecuteInitialLayoutPass();
 
-                target.Items = items;
+                target.ItemsSource = items;
 
                 lm.ExecuteLayoutPass();
 
@@ -415,7 +414,7 @@ namespace Avalonia.Controls.UnitTests
                     Height = 100,
                     Width = 50,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
-                    Items = items,
+                    ItemsSource = items,
                 };
                 wnd.Content = target;
 
@@ -450,7 +449,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
                     SelectionMode = SelectionMode.AlwaysSelected,
                 };
@@ -497,7 +496,7 @@ namespace Avalonia.Controls.UnitTests
                     AutoScrollToSelectedItem = true,
                     Width = 50,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
-                    Items = items,
+                    ItemsSource = items,
                 };
                 wnd.Content = target;
 
@@ -533,7 +532,7 @@ namespace Avalonia.Controls.UnitTests
         {
             var target = new ListBox
             {
-                [!ListBox.ItemsProperty] = new Binding("Items"),
+                [!ListBox.ItemsSourceProperty] = new Binding("Items"),
                 [!ListBox.SelectedItemsProperty] = new Binding("SelectedItems"),
             };
 
@@ -650,7 +649,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = ListBoxTemplate(),
-                Items = new[] { "Foo" },
+                ItemsSource = new[] { "Foo" },
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
@@ -672,7 +671,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = ListBoxTemplate(),
-                Items = items,
+                ItemsSource = items,
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
             };
 
@@ -703,7 +702,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = ListBoxTemplate(),
-                Items = items,
+                ItemsSource = items,
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
                 AutoScrollToSelectedItem = true,
                 SelectedIndex = 1,
@@ -749,7 +748,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = ListBoxTemplate(),
-                    Items = items,
+                    ItemsSource = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
                     WrapSelection = true
                 };

tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 SelectionMode = SelectionMode.Multiple
             };
 
@@ -41,7 +41,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 SelectionMode = SelectionMode.Multiple
             };
 
@@ -64,7 +64,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 SelectionMode = SelectionMode.Multiple
             };
 

tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs

@@ -26,7 +26,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
             };
 
             ApplyTemplate(target);
@@ -45,7 +45,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
             };
 
             ApplyTemplate(target);
@@ -64,7 +64,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
             };
 
             ApplyTemplate(target);
@@ -86,7 +86,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 ApplyTemplate(target);
@@ -116,7 +116,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 ApplyTemplate(target);
@@ -134,7 +134,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 ApplyTemplate(target);
@@ -154,7 +154,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                     SelectionMode = SelectionMode.Single | SelectionMode.Toggle,
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
@@ -174,7 +174,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                     SelectionMode = SelectionMode.Toggle,
                 };
 
@@ -196,7 +196,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                     SelectionMode = SelectionMode.Toggle | SelectionMode.AlwaysSelected,
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
@@ -217,7 +217,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ListBox
                 {
                     Template = new FuncControlTemplate(CreateListBoxTemplate),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                     SelectionMode = SelectionMode.Single | SelectionMode.Toggle,
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
@@ -236,7 +236,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new ListBox
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
             };
 
             ApplyTemplate(target);
@@ -259,7 +259,7 @@ namespace Avalonia.Controls.UnitTests
             {
                 Template = new FuncControlTemplate(CreateListBoxTemplate),
                 DataContext = viewModel,
-                Items = viewModel.Items
+                ItemsSource = viewModel.Items
             };
 
             target.Bind(ListBox.SelectedItemProperty,

tests/Avalonia.Controls.UnitTests/MenuItemTests.cs

@@ -191,7 +191,7 @@ namespace Avalonia.Controls.UnitTests
                     return true;
                 });
                 var target = new MenuItem();
-                var contextMenu = new ContextMenu { Items = new AvaloniaList<MenuItem> { target } };
+                var contextMenu = new ContextMenu { Items = { target } };
                 var window = new Window { Content = new Panel { ContextMenu = contextMenu } };
                 window.ApplyStyling();
                 window.ApplyTemplate();
@@ -270,8 +270,8 @@ namespace Avalonia.Controls.UnitTests
                     return true;
                 });
                 var target = new MenuItem();
-                var parentMenuItem = new MenuItem { Items = new AvaloniaList<MenuItem> { target } };
-                var contextMenu = new ContextMenu { Items = new AvaloniaList<MenuItem> { parentMenuItem } };
+                var parentMenuItem = new MenuItem { Items = { target } };
+                var contextMenu = new ContextMenu { Items = { parentMenuItem } };
                 var window = new Window { Content = new Panel { ContextMenu = contextMenu } };
                 window.ApplyStyling();
                 window.ApplyTemplate();
@@ -317,12 +317,12 @@ namespace Avalonia.Controls.UnitTests
                 MenuItem childMenu2;
                 var menu = new Menu
                 {
-                    Items = new[]
+                    Items =
                     {
                         (topLevelMenu = new MenuItem
                         {
                             Header = "Foo",
-                            Items = new[]
+                            Items =
                             {
                                 (childMenu1 = new MenuItem { Header = "Bar" }),
                                 (childMenu2 = new MenuItem { Header = "Baz" }),

tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs

@@ -114,7 +114,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
                 var panel = Assert.IsType<StackPanel>(target.Panel);
 
                 var newItems = new[] { "qux", "quux", "corge" };
-                itemsControl.Items = newItems;
+                itemsControl.ItemsSource = newItems;
                 root.LayoutManager.ExecuteLayoutPass();
 
                 AssertContainers(panel, newItems);

tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs

@@ -395,7 +395,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var item = new Border();
                 var root = PreparedWindow(target = new PopupItemsControl
                 {
-                    Items = new[] { item },
+                    Items = { item },
                     Template = new FuncControlTemplate<PopupItemsControl>(PopupItemsControlTemplate),
                 }); ;
                 root.Show();
@@ -490,7 +490,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var item = new Border();
                 var root = PreparedWindow(target = new PopupItemsControl
                 {
-                    Items = new[] { item },
+                    Items = { item },
                     Template = new FuncControlTemplate<PopupItemsControl>(PopupItemsControlTemplate),
                 });
                 root.Show();

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs

@@ -43,7 +43,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -61,7 +61,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -82,7 +82,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -105,7 +105,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -127,7 +127,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new ListBox();
             target.BeginInit();
-            target.Items = items;
+            target.ItemsSource = items;
             target.Template = Template();
             target.EndInit();
 
@@ -144,7 +144,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             };
 
             var target = new ListBox();
-            target.Items = items;
+            target.ItemsSource = items;
             target.Template = Template();
             target.DataContext = new object();
 
@@ -163,7 +163,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox();
             target.BeginInit();
             target.SelectionMode = SelectionMode.Single | SelectionMode.AlwaysSelected;
-            target.Items = items;
+            target.ItemsSource = items;
             target.Template = Template();
             target.EndInit();
 
@@ -184,7 +184,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             listBox.SelectedIndex = 1;
             var items = new AvaloniaList<string>();
-            listBox.Items = items;
+            listBox.ItemsSource = items;
             items.Add("A");
             items.Add("B");
             items.Add("C");
@@ -202,7 +202,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var listBox = new ListBox
             {
                 SelectionMode = SelectionMode.Single,
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 SelectedIndex = 1
             };
 
@@ -220,7 +220,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var listBox = new ListBox
             {
                 SelectionMode = SelectionMode.Single,
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 SelectedIndex = 2
             };
 
@@ -240,7 +240,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var listBox = new ListBox
             {
                 SelectionMode = SelectionMode.Single,
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 SelectedItem = "bar"
             };
 
@@ -259,7 +259,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var listBox = new ListBox
             {
                 SelectionMode = SelectionMode.Multiple,
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
             };
 
             var selected = new[] { "foo", "bar" };
@@ -282,7 +282,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var listBox = new ListBox
             {
                 SelectionMode = SelectionMode.Multiple,
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
             };
 
             var selected = new[] { "foo", "bar" };
@@ -308,7 +308,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             {
                 SelectionMode = SelectionMode.Single | SelectionMode.AlwaysSelected,
 
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 SelectedIndex = 1
             };
 
@@ -331,7 +331,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -353,7 +353,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -376,7 +376,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -403,7 +403,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -430,7 +430,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -451,7 +451,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -487,7 +487,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -509,7 +509,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -519,7 +519,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(items[1], target.SelectedItem);
             Assert.Equal(1, target.SelectedIndex);
 
-            target.Items = null;
+            target.ItemsSource = null;
 
             Assert.Null(target.SelectedItem);
             Assert.Equal(-1, target.SelectedIndex);
@@ -536,7 +536,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -575,7 +575,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
@@ -611,7 +611,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl();
             target.BeginInit();
-            target.Items = items;
+            target.ItemsSource = items;
             target.Template = Template();
             target.EndInit();
 
@@ -648,7 +648,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -684,7 +684,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -722,7 +722,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -749,7 +749,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -779,7 +779,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -807,7 +807,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -839,7 +839,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -868,7 +868,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedIndex = 1,
             };
@@ -896,7 +896,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -932,7 +932,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -968,7 +968,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
@@ -1004,7 +1004,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
@@ -1041,7 +1041,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -1078,7 +1078,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             ((ISupportInitialize)target).BeginInit();
             target.SelectedIndex = 1;
-            target.Items = items;
+            target.ItemsSource = items;
             ((ISupportInitialize)target).EndInit();
 
             Prepare(target);
@@ -1096,7 +1096,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             ((ISupportInitialize)target).BeginInit();
             target.SelectedItem = "Bar";
-            target.Items = items;
+            target.ItemsSource = items;
             ((ISupportInitialize)target).EndInit();
 
             Prepare(target);
@@ -1127,7 +1127,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var itemsBinding = new Binding("Child.Items");
             var selectedBinding = new Binding("Child.SelectedItem");
 
-            target.Bind(SelectingItemsControl.ItemsProperty, itemsBinding);
+            target.Bind(SelectingItemsControl.ItemsSourceProperty, itemsBinding);
             target.Bind(SelectingItemsControl.SelectedItemProperty, selectedBinding);
 
             Assert.Equal(1, target.SelectedIndex);
@@ -1163,13 +1163,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var root = new SelectingItemsControl
             {
                 Template = Template(),
-                Items = new Control[]
+                ItemsSource = new Control[]
                 {
                     new Border(),
                     nested = new ListBox
                     {
                         Template = Template(),
-                        Items = new[] { "foo", "bar" },
+                        ItemsSource = new[] { "foo", "bar" },
                         SelectedIndex = 1,
                     }
                 },
@@ -1197,7 +1197,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz " },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz " },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 Prepare(target);
@@ -1221,7 +1221,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = items,
+                    ItemsSource = items,
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 Prepare(target);
@@ -1245,7 +1245,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             itemsMock.Object.AddRange(new[] { "Foo", "Bar", "Baz" });
             var target = new SelectingItemsControl
             {
-                Items = itemsMock.Object
+                ItemsSource = itemsMock.Object
             };
 
             target.SelectedIndex = 1;
@@ -1268,7 +1268,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             target.BeginInit();
             root.Child = target;
 
-            DelayedBinding.Add(target, ItemsControl.ItemsProperty, new Binding(nameof(RootWithItems.Items)));
+            DelayedBinding.Add(target, ItemsControl.ItemsSourceProperty, new Binding(nameof(RootWithItems.Items)));
             DelayedBinding.Add(target, ListBox.SelectedItemProperty, new Binding(nameof(RootWithItems.Selected)));
             target.EndInit();
             root.EndInit();
@@ -1299,7 +1299,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var itemsBinding = new Binding("Child.Items");
             var selectedIndBinding = new Binding("Child.SelectedIndex");
 
-            target.Bind(SelectingItemsControl.ItemsProperty, itemsBinding);
+            target.Bind(SelectingItemsControl.ItemsSourceProperty, itemsBinding);
             target.Bind(SelectingItemsControl.SelectedIndexProperty, selectedIndBinding);
 
             Assert.Equal(1, target.SelectedIndex);
@@ -1318,7 +1318,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 Prepare(target);
@@ -1336,7 +1336,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 Prepare(target);
@@ -1359,7 +1359,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 1,
             };
 
@@ -1384,7 +1384,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 1,
             };
 
@@ -1405,14 +1405,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var other = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
 
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 [!ListBox.SelectedIndexProperty] = other[!ListBox.SelectedIndexProperty],
             };
 
@@ -1434,14 +1434,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var other = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
 
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 [!ListBox.SelectedItemProperty] = other[!ListBox.SelectedItemProperty],
             };
 
@@ -1468,7 +1468,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 1,
             };
 
@@ -1493,7 +1493,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
             };
 
             var raised = false;
@@ -1518,7 +1518,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
             };
 
             var raised = false;
@@ -1540,7 +1540,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 var target = new ListBox
                 {
-                    Items = items,
+                    ItemsSource = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) =>
                         new TextBlock
                         {
@@ -1582,7 +1582,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 2,
             };
 
@@ -1614,7 +1614,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectedIndex = 2,
             };
 
@@ -1645,7 +1645,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 AutoScrollToSelectedItem = false,
             };
 
@@ -1671,7 +1671,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             target.BeginInit();
             target.Template = Template();
-            target.Items = new[] { "Foo", "Bar", "Baz" };
+            target.ItemsSource = new[] { "Foo", "Bar", "Baz" };
             target.SelectedItems = selectedItems;
             target.SelectedItem = "Bar";
             target.EndInit();
@@ -1691,7 +1691,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem { Focusable = false },
                     new ListBoxItem { Focusable = false },
@@ -1713,7 +1713,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem(),
                     new ListBoxItem { Focusable = false },
@@ -1733,7 +1733,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem { Focusable = false },
                     new ListBoxItem(),
@@ -1753,7 +1753,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem { Focusable = false },
                     new ListBoxItem { Focusable = false },
@@ -1776,7 +1776,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem { Focusable = false },
                     new ListBoxItem { Focusable = false },
@@ -1800,7 +1800,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[]
+                Items =
                 {
                     new ListBoxItem(),
                     new ListBoxItem { IsEnabled = false },
@@ -1831,7 +1831,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 second
             };
 
-            target.Items = items;
+            target.ItemsSource = items;
 
             Prepare(target);
 
@@ -1878,7 +1878,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new ListBox
             {
-                [!ListBox.ItemsProperty] = new Binding("Items"),
+                [!ListBox.ItemsSourceProperty] = new Binding("Items"),
                 [!ListBox.SelectedIndexProperty] = new Binding("SelectedIndex"),
                 DataContext = vm,
             };
@@ -1906,7 +1906,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new ListBox
             {
-                [!ListBox.ItemsProperty] = new Binding("Items"),
+                [!ListBox.ItemsSourceProperty] = new Binding("Items"),
                 [!ListBox.SelectedItemsProperty] = new Binding("SelectedItems"),
                 DataContext = vm,
             };
@@ -1926,7 +1926,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             using var app = Start();
             var target = new SelectingItemsControl
             {
-                Items = new[] { "foo", "bar", "baz"},
+                ItemsSource = new[] { "foo", "bar", "baz"},
                 SelectedItem = "bar",
             };
 
@@ -1935,7 +1935,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(1, target.SelectedIndex);
             Assert.Equal("bar", target.SelectedItem);
 
-            target.Items = new[] { "qux", "foo", "bar" };
+            target.ItemsSource = new[] { "qux", "foo", "bar" };
 
             Assert.Equal(2, target.SelectedIndex);
             Assert.Equal("bar", target.SelectedItem);
@@ -1947,7 +1947,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             using var app = Start();
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
             };
 
             var raised = 0;
@@ -1976,7 +1976,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             using var app = Start();
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
             };
 
             var raised = 0;
@@ -2007,13 +2007,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
             // Simulates problem with TabStrip and Carousel with bound SelectedIndex.
             var tabStrip = new TestSelector 
             { 
-                Items = items, 
+                ItemsSource = items, 
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
 
             var carousel = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 [!Carousel.SelectedIndexProperty] = tabStrip[!TabStrip.SelectedIndexProperty],
             };
 
@@ -2048,13 +2048,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
             // Simulates problem with TabStrip and Carousel with bound SelectedItem.
             var tabStrip = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.AlwaysSelected,
             };
 
             var carousel = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 [!Carousel.SelectedItemProperty] = tabStrip[!TabStrip.SelectedItemProperty],
             };
 
@@ -2100,7 +2100,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 var target = new SelectingItemsControl
                 {
-                    Items = items, 
+                    ItemsSource = items, 
                     Template = Template(), 
                     IsTextSearchEnabled = false
                 };

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs

@@ -16,7 +16,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -32,7 +32,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = new AvaloniaList<string>();
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -50,7 +50,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = new ResetOnAdd();
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -68,7 +68,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -87,7 +87,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 
@@ -106,7 +106,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = new AvaloniaList<string>(new[] { "foo", "bar" });
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
             };
 

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs

@@ -27,7 +27,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -42,7 +42,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -57,7 +57,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -75,7 +75,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -94,7 +94,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             // Issue #2565.
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -112,7 +112,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -129,7 +129,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -157,7 +157,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -179,7 +179,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -200,26 +200,23 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Adding_SelectedItems_Should_Set_Item_IsSelected()
         {
-            var items = new[]
-            {
-                new ListBoxItem(),
-                new ListBoxItem(),
-                new ListBoxItem(),
-            };
-
             var target = new TestSelector
             {
-                Items = items,
+                Items = 
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                },
                 Template = Template(),
             };
 
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
-            target.SelectedItems.Add(items[0]);
-            target.SelectedItems.Add(items[1]);
-
-            var foo = target.Presenter.Panel.Children[0];
+            target.SelectedItems.Add(target.Items[0]);
+            target.SelectedItems.Add(target.Items[1]);
 
+            var items = target.Items.Cast<ListBoxItem>().ToList();
             Assert.True(items[0].IsSelected);
             Assert.True(items[1].IsSelected);
             Assert.False(items[2].IsSelected);
@@ -228,23 +225,22 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Assigning_SelectedItems_Should_Set_Item_IsSelected()
         {
-            var items = new[]
-            {
-                new ListBoxItem(),
-                new ListBoxItem(),
-                new ListBoxItem(),
-            };
-
             var target = new TestSelector
             {
-                Items = items,
+                Items =
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                },
                 Template = Template(),
             };
 
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
-            target.SelectedItems = new AvaloniaList<object> { items[0], items[1] };
+            target.SelectedItems = new AvaloniaList<object> { target.Items[0], target.Items[1] };
 
+            var items = target.Items.Cast<ListBoxItem>().ToList();
             Assert.True(items[0].IsSelected);
             Assert.True(items[1].IsSelected);
             Assert.False(items[2].IsSelected);
@@ -253,25 +249,24 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Removing_SelectedItems_Should_Clear_Item_IsSelected()
         {
-            var items = new[]
-            {
-                new ListBoxItem(),
-                new ListBoxItem(),
-                new ListBoxItem(),
-            };
-
             var target = new TestSelector
             {
-                Items = items,
+                Items =
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                },
                 Template = Template(),
             };
 
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
-            target.SelectedItems.Add(items[0]);
-            target.SelectedItems.Add(items[1]);
-            target.SelectedItems.Remove(items[1]);
+            target.SelectedItems.Add(target.Items[0]);
+            target.SelectedItems.Add(target.Items[1]);
+            target.SelectedItems.Remove(target.Items[1]);
 
+            var items = target.Items.Cast<ListBoxItem>().ToList();
             Assert.True(items[0].IsSelected);
             Assert.False(items[1].IsSelected);
         }
@@ -279,25 +274,24 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Reassigning_SelectedItems_Should_Clear_Item_IsSelected()
         {
-            var items = new[]
-            {
-                new ListBoxItem(),
-                new ListBoxItem(),
-                new ListBoxItem(),
-            };
-
             var target = new TestSelector
             {
-                Items = items,
+                Items = 
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                },
                 Template = Template(),
             };
 
             target.ApplyTemplate();
-            target.SelectedItems.Add(items[0]);
-            target.SelectedItems.Add(items[1]);
+            target.SelectedItems.Add(target.Items[0]);
+            target.SelectedItems.Add(target.Items[1]);
 
-            target.SelectedItems = new AvaloniaList<object> { items[0], items[1] };
+            target.SelectedItems = new AvaloniaList<object> { target.Items[0], target.Items[1] };
 
+            var items = target.Items.Cast<ListBoxItem>().ToList();
             Assert.False(items[0].IsSelected);
             Assert.False(items[1].IsSelected);
         }
@@ -307,7 +301,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -329,7 +323,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[]
+                ItemsSource = new[]
                 {
                     "foo",
                     "bar",
@@ -353,7 +347,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[]
+                ItemsSource = new[]
                 {
                     "foo",
                     "bar",
@@ -378,7 +372,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[]
+                ItemsSource = new[]
                 {
                     "foo",
                     "bar",
@@ -404,7 +398,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz", "qux" },
+                ItemsSource = new[] { "foo", "bar", "baz", "qux" },
                 Template = Template(),
                 SelectedIndex = 0,
                 SelectionMode = SelectionMode.Multiple,
@@ -427,7 +421,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz", "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz", "foo", "bar", "baz" },
                 Template = Template(),
                 SelectedIndex = 0,
                 SelectionMode = SelectionMode.Multiple,
@@ -450,7 +444,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -471,7 +465,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -536,8 +530,8 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Mode = BindingMode.OneWay,
             };
 
-            // Bind Items and SelectedItems to the VM.
-            target.Bind(TestSelector.ItemsProperty, itemsBinding);
+            // Bind ItemsSource and SelectedItems to the VM.
+            target.Bind(TestSelector.ItemsSourceProperty, itemsBinding);
             target.Bind(TestSelector.SelectedItemsProperty, selectedItemsBinding);
 
             // Set DataContext and SelectedIndex
@@ -576,8 +570,8 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Mode = BindingMode.OneWay,
             };
 
-            // Bind Items and Selection to the VM.
-            target.Bind(TestSelector.ItemsProperty, itemsBinding);
+            // Bind ItemsSource and Selection to the VM.
+            target.Bind(TestSelector.ItemsSourceProperty, itemsBinding);
             target.Bind(TestSelector.SelectionProperty, selectionBinding);
 
             // Set DataContext and SelectedIndex
@@ -610,9 +604,9 @@ namespace Avalonia.Controls.UnitTests.Primitives
             };
 
             var itemsBinding = new Binding { Path = "Items" };
-            target.Bind(TestSelector.ItemsProperty, itemsBinding);
+            target.Bind(TestSelector.ItemsSourceProperty, itemsBinding);
 
-            Assert.Same(data.Items, target.Items);
+            Assert.Same(data.Items, target.ItemsSource);
 
             target.SelectedItems.Add("bar");
             target.DataContext = null;
@@ -629,7 +623,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             {
                 DataContext = items,
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
             };
 
             var called = false;
@@ -653,7 +647,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedItem = "bar",
             };
@@ -679,7 +673,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedItem = "bar",
             };
@@ -708,7 +702,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -733,7 +727,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Qux" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -791,7 +785,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Qux" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -825,7 +819,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -856,7 +850,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -884,7 +878,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -912,7 +906,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -940,7 +934,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Qux" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -992,7 +986,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
                     Height = 100,
@@ -1026,7 +1020,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[] { "Foo", "Bar", "Baz" },
+                ItemsSource = new[] { "Foo", "Bar", "Baz" },
                 SelectionMode = SelectionMode.Multiple,
             };
 
@@ -1045,7 +1039,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[] { "Foo", "Bar", "Baz" },
+                ItemsSource = new[] { "Foo", "Bar", "Baz" },
                 SelectionMode = SelectionMode.Multiple,
             };
 
@@ -1059,7 +1053,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             target.SelectAll();
 
             Assert.NotNull(receivedArgs);
-            Assert.Equal(target.Items, receivedArgs.AddedItems);
+            Assert.Equal(target.ItemsSource, receivedArgs.AddedItems);
             Assert.Empty(receivedArgs.RemovedItems);
         }
 
@@ -1069,7 +1063,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[] { "Foo", "Bar", "Baz" },
+                ItemsSource = new[] { "Foo", "Bar", "Baz" },
                 SelectionMode = SelectionMode.Multiple,
                 SelectedIndex = 0,
             };
@@ -1089,7 +1083,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
+                ItemsSource = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                 SelectionMode = SelectionMode.Multiple,
             };
 
@@ -1113,7 +1107,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.Multiple,
                 Width = 100,
                 Height = 100,
@@ -1145,7 +1139,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new TestSelector
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.Multiple,
             };
 
@@ -1178,7 +1172,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.Multiple,
                 Width = 100,
                 Height = 100,
@@ -1209,7 +1203,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var target = new ListBox
             {
                 Template = Template(),
-                Items = items,
+                ItemsSource = items,
                 SelectionMode = SelectionMode.Multiple,
                 Width = 100,
                 Height = 100,
@@ -1232,7 +1226,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
@@ -1262,7 +1256,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
@@ -1290,7 +1284,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
@@ -1315,27 +1309,25 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Adding_Selected_ItemContainers_Should_Update_Selection()
         {
-            var items = new AvaloniaList<ItemContainer>(new[]
-            {
-                new ItemContainer(),
-                new ItemContainer(),
-            });
-
             var target = new TestSelector
             {
-                Items = items,
+                Items =
+                {
+                    new ItemContainer(),
+                    new ItemContainer(),
+                },
                 SelectionMode = SelectionMode.Multiple,
                 Template = Template(),
             };
 
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
-            items.Add(new ItemContainer { IsSelected = true });
-            items.Add(new ItemContainer { IsSelected = true });
+            target.Items.Add(new ItemContainer { IsSelected = true });
+            target.Items.Add(new ItemContainer { IsSelected = true });
 
             Assert.Equal(2, target.SelectedIndex);
-            Assert.Equal(items[2], target.SelectedItem);
-            Assert.Equal(new[] { items[2], items[3] }, target.SelectedItems);
+            Assert.Equal(target.Items[2], target.SelectedItem);
+            Assert.Equal(new[] { target.Items[2], target.Items[3] }, target.SelectedItems);
         }
 
         [Fact]
@@ -1346,7 +1338,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
@@ -1373,7 +1365,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var target = new ListBox
                 {
                     Template = Template(),
-                    Items = new[] { "Foo", "Bar", "Baz" },
+                    ItemsSource = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
                     Width = 100,
@@ -1397,7 +1389,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -1412,7 +1404,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -1429,7 +1421,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -1442,14 +1434,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
             var selection = new SelectionModel<string>();
             target.Selection = selection;
 
-            Assert.Same(target.Items, selection.Source);
+            Assert.Same(target.ItemsSource, selection.Source);
         }
 
         [Fact]
@@ -1457,7 +1449,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -1478,7 +1470,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar", "baz" },
+                ItemsSource = new[] { "foo", "bar", "baz" },
                 Template = Template(),
             };
 
@@ -1499,7 +1491,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         {
             var target = new TestSelector
             {
-                Items = new[] { "foo", "bar" },
+                ItemsSource = new[] { "foo", "bar" },
                 Template = Template(),
             };
 
@@ -1514,16 +1506,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void Assigning_Selection_Should_Set_Item_IsSelected()
         {
-            var items = new[]
-            {
-                new ListBoxItem(),
-                new ListBoxItem(),
-                new ListBoxItem(),
-            };
-
             var target = new TestSelector
             {
-                Items = items,
+                Items =
+                {
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                    new ListBoxItem(),
+                },
                 Template = Template(),
             };
 
@@ -1534,6 +1524,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             selection.SelectRange(0, 1);
             target.Selection = selection;
 
+            var items = target.Items.Cast<ListBoxItem>().ToList();
             Assert.True(items[0].IsSelected);
             Assert.True(items[1].IsSelected);
             Assert.False(items[2].IsSelected);
@@ -1546,7 +1537,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
             var target = new TestSelector
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedItem = "bar",
             };

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_SelectedValue.cs

@@ -21,7 +21,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 SelectedValueBinding = new Binding("Name"),
                 Template = Template()
             };
@@ -37,7 +37,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 SelectedValueBinding = new Binding("Name"),
                 Template = Template()
             };
@@ -53,7 +53,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new ListBox
             {
-                Items = items,
+                ItemsSource = items,
                 SelectedValueBinding = new Binding("Name"),
                 Template = Template()
             };
@@ -78,7 +78,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var items = TestClass.GetItems();
                 var sic = new SelectingItemsControl
                 {
-                    Items = items,
+                    ItemsSource = items,
                     SelectedValueBinding = new Binding("Name"),
                     Template = Template()
                 };
@@ -99,7 +99,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var items = TestClass.GetItems();
                 var sic = new SelectingItemsControl
                 {
-                    Items = items,
+                    ItemsSource = items,
                     SelectedValueBinding = new Binding("Name"),
                     Template = Template()
                 };
@@ -120,7 +120,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var items = TestClass.GetItems();
                 var sic = new SelectingItemsControl
                 {
-                    Items = items,
+                    ItemsSource = items,
                     SelectedValueBinding = new Binding("Name"),
                     Template = Template()
                 };
@@ -143,7 +143,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template()
             };
 
@@ -158,7 +158,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedValueBinding = new Binding("Name"),
                 SelectedValue = "Item2"
@@ -176,7 +176,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedValueBinding = new Binding("Name"),
                 SelectedValue = "Item2"
@@ -197,7 +197,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var items = TestClass.GetItems();
                 var sic = new SelectingItemsControl
                 {
-                    Items = items,
+                    ItemsSource = items,
                     Template = Template(),
                     SelectedValueBinding = new Binding("Name"),
                     SelectedValue = "Item2"
@@ -205,7 +205,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 Prepare(sic);
 
-                sic.Items = new List<TestClass>
+                sic.ItemsSource = new List<TestClass>
                 {
                     new TestClass("NewItem", string.Empty)
                 };
@@ -224,7 +224,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 var items = TestClass.GetItems();
                 var sic = new SelectingItemsControl
                 {
-                    Items = items,
+                    ItemsSource = items,
                     Template = Template(),
                     SelectedValueBinding = new Binding("Name"),
                 };
@@ -250,7 +250,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             var items = TestClass.GetItems();
             var sic = new SelectingItemsControl
             {
-                Items = items,
+                ItemsSource = items,
                 Template = Template(),
                 SelectedValueBinding = new Binding("Name"),
                 SelectedValue = "Item2"

tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs

@@ -14,90 +14,84 @@ namespace Avalonia.Controls.UnitTests.Primitives
         [Fact]
         public void First_Tab_Should_Be_Selected_By_Default()
         {
-            var items = new[]
-            {
-                new TabItem
-                {
-                    Name = "first"
-                },
-                new TabItem
-                {
-                    Name = "second"
-                },
-            };
-
             var target = new TabStrip
             {
                 Template = new FuncControlTemplate<TabStrip>(CreateTabStripTemplate),
-                Items = items,
+                Items =
+                {
+                    new TabItem
+                    {
+                        Name = "first"
+                    },
+                    new TabItem
+                    {
+                        Name = "second"
+                    },
+                }
             };
 
             target.ApplyTemplate();
 
             Assert.Equal(0, target.SelectedIndex);
-            Assert.Same(items[0], target.SelectedItem);
+            Assert.Same(target.Items[0], target.SelectedItem);
         }
 
         [Fact]
         public void Setting_SelectedItem_Should_Set_Selection()
         {
-            var items = new[]
-            {
-                new TabItem
-                {
-                    Name = "first"
-                },
-                new TabItem
-                {
-                    Name = "second"
-                },
-            };
-
             var target = new TabStrip
             {
                 Template = new FuncControlTemplate<TabStrip>(CreateTabStripTemplate),
-                Items = items,
-                SelectedItem = items[1],
+                Items =
+                {
+                    new TabItem
+                    {
+                        Name = "first"
+                    },
+                    new TabItem
+                    {
+                        Name = "second"
+                    },
+                },             
             };
 
+            target.SelectedItem = target.Items[1];
             target.ApplyTemplate();
 
             Assert.Equal(1, target.SelectedIndex);
-            Assert.Same(items[1], target.SelectedItem);
+            Assert.Same(target.Items[1], target.SelectedItem);
         }
 
         [Fact]
         public void Removing_Selected_Should_Select_First()
         {
-            var items = new ObservableCollection<TabItem>()
-            {
-                new TabItem
-                {
-                    Name = "first"
-                },
-                new TabItem
-                {
-                    Name = "second"
-                },
-                new TabItem
-                {
-                    Name = "3rd"
-                },
-            };
-
             var target = new TabStrip
             {
                 Template = new FuncControlTemplate<TabStrip>(CreateTabStripTemplate),
-                Items = items
+                Items =
+                {
+                    new TabItem
+                    {
+                        Name = "first"
+                    },
+                    new TabItem
+                    {
+                        Name = "second"
+                    },
+                    new TabItem
+                    {
+                        Name = "3rd"
+                    },
+                }
             };
 
             target.ApplyTemplate();
-            target.SelectedItem = items[1];
-            Assert.Same(items[1], target.SelectedItem);
-            items.RemoveAt(1);
+            target.SelectedItem = target.Items[1];
+            Assert.Same(target.Items[1], target.SelectedItem);
+            target.Items.RemoveAt(1);
 
             Assert.Equal(0, target.SelectedIndex);
-            Assert.Same(items[0], target.SelectedItem);
+            Assert.Same(target.Items[0], target.SelectedItem);
             Assert.Same("first", ((TabItem)target.SelectedItem).Name);
         }
 

tests/Avalonia.Controls.UnitTests/TabControlTests.cs

@@ -24,7 +24,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = new[]
+                Items =
                 {
                     (selected = new TabItem
                     {
@@ -48,21 +48,17 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void Pre_Selecting_TabItem_Should_Set_SelectedContent_After_It_Was_Added()
         {
+            const string secondContent = "Second";
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
+                Items =
+                {
+                    new TabItem { Header = "First"},
+                    new TabItem { Header = "Second", Content = secondContent, IsSelected = true }
+                },
             };
 
-            const string secondContent = "Second";
-
-            var items = new AvaloniaList<object>
-            {
-                new TabItem { Header = "First"},
-                new TabItem { Header = "Second", Content = secondContent, IsSelected = true }
-            };
-
-            target.Items = items;
-
             ApplyTemplate(target);
 
             Assert.Equal(secondContent, target.SelectedContent);
@@ -74,7 +70,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = 
+                Items =
                 {
                     new TabItem
                     {
@@ -87,89 +83,89 @@ namespace Avalonia.Controls.UnitTests
                 }
             };
 
-            Assert.Equal(target.Items.Cast<ILogical>(), target.GetLogicalChildren());
+            Assert.Equal(target.Items, target.GetLogicalChildren().ToList());
             target.ApplyTemplate();
-            Assert.Equal(target.Items.Cast<ILogical>(), target.GetLogicalChildren());
+            Assert.Equal(target.Items, target.GetLogicalChildren().ToList());
         }
 
         [Fact]
         public void Removal_Should_Set_First_Tab()
         {
-            var collection = new ObservableCollection<TabItem>()
-            {
-                new TabItem
-                {
-                    Name = "first",
-                    Content = "foo",
-                },
-                new TabItem
-                {
-                    Name = "second",
-                    Content = "bar",
-                },
-                new TabItem
-                {
-                    Name = "3rd",
-                    Content = "barf",
-                },
-            };
-
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = collection,
+                Items =
+                {
+                    new TabItem
+                    {
+                        Name = "first",
+                        Content = "foo",
+                    },
+                    new TabItem
+                    {
+                        Name = "second",
+                        Content = "bar",
+                    },
+                    new TabItem
+                    {
+                        Name = "3rd",
+                        Content = "barf",
+                    },
+                }
             };
 
             Prepare(target);
-            target.SelectedItem = collection[1];
+            target.SelectedItem = target.Items[1];
 
-            Assert.Same(collection[1], target.SelectedItem);
-            Assert.Equal(collection[1].Content, target.SelectedContent);
+            var item = Assert.IsType<TabItem>(target.Items[1]);
+            Assert.Same(item, target.SelectedItem);
+            Assert.Equal(item.Content, target.SelectedContent);
 
-            collection.RemoveAt(1);
+            target.Items.RemoveAt(1);
 
-            Assert.Same(collection[0], target.SelectedItem);
-            Assert.Equal(collection[0].Content, target.SelectedContent);
+            item = Assert.IsType<TabItem>(target.Items[0]);
+            Assert.Same(item, target.SelectedItem);
+            Assert.Equal(item.Content, target.SelectedContent);
         }
 
         [Fact]
         public void Removal_Should_Set_New_Item0_When_Item0_Selected()
         {
-            var collection = new ObservableCollection<TabItem>()
-            {
-                new TabItem
-                {
-                    Name = "first",
-                    Content = "foo",
-                },
-                new TabItem
-                {
-                    Name = "second",
-                    Content = "bar",
-                },
-                new TabItem
-                {
-                    Name = "3rd",
-                    Content = "barf",
-                },
-            };
-
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = collection,
+                Items =
+                {
+                    new TabItem
+                    {
+                        Name = "first",
+                        Content = "foo",
+                    },
+                    new TabItem
+                    {
+                        Name = "second",
+                        Content = "bar",
+                    },
+                    new TabItem
+                    {
+                        Name = "3rd",
+                        Content = "barf",
+                    },
+                }
             };
 
             Prepare(target);
-            target.SelectedItem = collection[0];
+            target.SelectedItem = target.Items[0];
 
-            Assert.Same(collection[0], target.SelectedItem);
-            Assert.Equal(collection[0].Content, target.SelectedContent);
+            var item = Assert.IsType<TabItem>(target.Items[0]);
+            Assert.Same(item, target.SelectedItem);
+            Assert.Equal(item.Content, target.SelectedContent);
 
-            collection.RemoveAt(0);
+            target.Items.RemoveAt(0);
 
-            Assert.Same(collection[0], target.SelectedItem);
-            Assert.Equal(collection[0].Content, target.SelectedContent);
+            item = Assert.IsType<TabItem>(target.Items[0]);
+            Assert.Same(item, target.SelectedItem);
+            Assert.Equal(item.Content, target.SelectedContent);
         }
 
         [Fact]
@@ -187,7 +183,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = collection,
+                ItemsSource = collection,
             };
 
             Prepare(target);
@@ -269,7 +265,7 @@ namespace Avalonia.Controls.UnitTests
                 {
                     new FuncDataTemplate<Item>((x, __) => new Button { Content = x })
                 },
-                Items = items,
+                ItemsSource = items,
             };
 
             ApplyTemplate(target);
@@ -311,16 +307,14 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void Non_IHeadered_Control_Items_Should_Be_Ignored()
         {
-            var items = new[]
-            {
-                new TextBlock { Text = "foo" },
-                new TextBlock { Text = "bar" },
-            };
-
             var target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = items,
+                Items =
+                {
+                    new TextBlock { Text = "foo" },
+                    new TextBlock { Text = "bar" },
+                },
             };
 
             ApplyTemplate(target);
@@ -341,7 +335,7 @@ namespace Avalonia.Controls.UnitTests
             TabControl target = new TabControl
             {
                 Template = TabControlTemplate(),
-                Items = new[]
+                Items =
                 {
                     new TabItem { Header = "Foo" },
                     new TabItem { Header = "Foo", Content = new Decorator() },
@@ -366,7 +360,7 @@ namespace Avalonia.Controls.UnitTests
                 Template = TabControlTemplate(),
                 ContentTemplate = new FuncDataTemplate<string>((x, _) =>
                     new TextBlock { Tag = "bar", Text = x }),
-                Items = new[] { "Foo" },
+                ItemsSource = new[] { "Foo" },
             };
             var root = new TestRoot(target);
 
@@ -390,7 +384,7 @@ namespace Avalonia.Controls.UnitTests
             {
                 Template = TabControlTemplate(),
                 DataContext = dataContext,
-                Items = new AvaloniaList<object> { tabItem }
+                Items = { tabItem }
             };
 
             ApplyTemplate(target);
@@ -407,7 +401,7 @@ namespace Avalonia.Controls.UnitTests
 <Window xmlns='https://github.com/avaloniaui'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
-    <TabControl Name='tabs' Items='{Binding Tabs}'/>
+    <TabControl Name='tabs' ItemsSource='{Binding Tabs}'/>
 </Window>";
                 var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
                 var tabControl = window.FindControl<TabControl>("tabs");
@@ -415,7 +409,7 @@ namespace Avalonia.Controls.UnitTests
                 tabControl.DataContext = new { Tabs = new List<string>() };
                 window.ApplyTemplate();
 
-                Assert.Equal(0, tabControl.Items.Count());
+                Assert.Equal(0, tabControl.ItemsSource.Count());
             }
         }
 

tests/Avalonia.Controls.UnitTests/TreeViewTests.cs

@@ -31,7 +31,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
+                ItemsSource = CreateTestTreeData(),
             };
 
             var root = new TestRoot(target);
@@ -54,7 +54,7 @@ namespace Avalonia.Controls.UnitTests
                 Child = target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
+                    ItemsSource = CreateTestTreeData(),
                     ItemTemplate = new FuncTreeDataTemplate<Node>(
                         (_, __) => new Canvas(),
                         x => x.Children),
@@ -82,7 +82,7 @@ namespace Avalonia.Controls.UnitTests
                 Child = target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
+                    ItemsSource = CreateTestTreeData(),
                     ItemContainerTheme = theme,
                     ItemTemplate = new FuncTreeDataTemplate<Node>(
                         (_, __) => new Canvas(),
@@ -112,7 +112,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
+                ItemsSource = CreateTestTreeData(),
             };
 
             var root = new TestRoot(target);
@@ -131,7 +131,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
+                ItemsSource = CreateTestTreeData(),
             };
 
             var root = new TestRoot(target);
@@ -151,7 +151,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
@@ -181,7 +181,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -212,7 +212,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree
+                    ItemsSource = tree
                 };
 
                 var visualRoot = new TestRoot();
@@ -247,7 +247,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree
+                    ItemsSource = tree
                 };
 
                 var visualRoot = new TestRoot();
@@ -287,7 +287,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -330,7 +330,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -367,7 +367,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -404,7 +404,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -455,7 +455,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -488,7 +488,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -521,7 +521,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -554,7 +554,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -591,7 +591,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -649,7 +649,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -686,7 +686,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -744,7 +744,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -781,7 +781,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -839,7 +839,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -876,7 +876,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -934,7 +934,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -985,7 +985,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -1036,7 +1036,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -1066,7 +1066,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                 };
 
                 var visualRoot = new TestRoot();
@@ -1105,7 +1105,7 @@ namespace Avalonia.Controls.UnitTests
                     DataContext = dataContext
                 };
 
-                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
+                target.Bind(TreeView.ItemsSourceProperty, new Binding("Items"));
                 target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
 
                 var visualRoot = new TestRoot();
@@ -1137,7 +1137,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = new[] { "Foo", "Bar", "Baz " },
+                ItemsSource = new[] { "Foo", "Bar", "Baz " },
             };
 
             ApplyTemplates(target);
@@ -1171,7 +1171,7 @@ namespace Avalonia.Controls.UnitTests
                 {
                     new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
                 },
-                Items = items,
+                ItemsSource = items,
             };
 
             ApplyTemplates(target);
@@ -1189,15 +1189,13 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void Control_Item_Should_Not_Be_NameScope()
         {
-            var items = new object[]
-            {
-                new TreeViewItem(),
-            };
-
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = items,
+                Items =
+                {
+                    new TreeViewItem(),
+                }
             };
 
             target.ApplyTemplate();
@@ -1215,7 +1213,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = data,
+                ItemsSource = data,
             };
 
             var root = new TestRoot(target);
@@ -1256,7 +1254,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = data,
+                    ItemsSource = data,
                 };
 
                 var button = new Button();
@@ -1302,7 +1300,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = data,
+                    ItemsSource = data,
                     SelectedItem = selectedNode
                 };
 
@@ -1341,7 +1339,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -1379,7 +1377,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -1426,7 +1424,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple
                 };
 
@@ -1473,7 +1471,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple,
                 };
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
@@ -1503,7 +1501,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple,
                 };
 
@@ -1542,7 +1540,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple,
                 };
 
@@ -1575,7 +1573,7 @@ namespace Avalonia.Controls.UnitTests
                 var target = new TreeView
                 {
                     Template = CreateTreeViewTemplate(),
-                    Items = tree,
+                    ItemsSource = tree,
                     SelectionMode = SelectionMode.Multiple,
                 };
 
@@ -1606,7 +1604,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             var visualRoot = new TestRoot();
@@ -1630,7 +1628,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new DerivedTreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             var visualRoot = new TestRoot();
@@ -1655,7 +1653,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             var visualRoot = new TestRoot();
@@ -1688,11 +1686,11 @@ namespace Avalonia.Controls.UnitTests
                 {
                     Template = CreateTreeViewTemplate(),
                     SelectionMode = SelectionMode.Multiple,
-                    Items = new List<Node>
-                {
-                    new Node { Value = "Root1", },
-                    new Node { Value = "Root2", },
-                },
+                    ItemsSource = new List<Node>
+                    {
+                        new Node { Value = "Root1", },
+                        new Node { Value = "Root2", },
+                    },
                 };
 
                 var visualRoot = new TestRoot
@@ -1726,7 +1724,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             var root = new TestRoot();
@@ -1760,7 +1758,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new TreeView
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             var root = new TestRoot();
@@ -1788,7 +1786,7 @@ namespace Avalonia.Controls.UnitTests
             var target = new DerivedTreeViewWithDerivedTreeViewItems
             {
                 Template = CreateTreeViewTemplate(),
-                Items = tree,
+                ItemsSource = tree,
             };
 
             ApplyTemplates(target);
@@ -1825,7 +1823,7 @@ namespace Avalonia.Controls.UnitTests
 
             foreach (var index in indexes)
             {
-                var item = ((IList)c.Items)[index];
+                var item = c.ItemsView[index];
                 c = (ItemsControl)target.TreeContainerFromItem(item);
             }
 

tests/Avalonia.Controls.UnitTests/Utils/HotKeyManagerTests.cs

@@ -263,7 +263,7 @@ namespace Avalonia.Controls.UnitTests.Utils
             };
             var rootMenu = new Menu();
 
-            rootMenu.Items = new[] { menuitem };
+            rootMenu.Items.Add(menuitem);
 
             root.Content = rootMenu;
             return menuitem;
@@ -288,7 +288,7 @@ namespace Avalonia.Controls.UnitTests.Utils
             };
             var rootMenu = new Menu();
 
-            rootMenu.Items = new[] { menuitem };
+            rootMenu.Items.Add(menuitem);
 
             root.Content = rootMenu;
             return menuitem;

tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs

@@ -50,7 +50,7 @@ namespace Avalonia.Controls.UnitTests
 
             Assert.Empty(itemsControl.GetRealizedContainers());
 
-            itemsControl.Items = new[] { "foo", "bar" };
+            itemsControl.ItemsSource = new[] { "foo", "bar" };
             Layout(target);
 
             AssertRealizedItems(target, itemsControl, 0, 2);

tests/Avalonia.LeakTests/ControlTests.cs

@@ -353,7 +353,7 @@ namespace Avalonia.LeakTests
                                     (x, _) => new TextBlock { Text = x.Name },
                                     x => x.Children)
                             },
-                            Items = nodes
+                            ItemsSource = nodes
                         }
                     };
 
@@ -428,7 +428,7 @@ namespace Avalonia.LeakTests
                     {
                         Content = new TabControl
                         {
-                            Items = new[] { new TabItem() }
+                            ItemsSource = new[] { new TabItem() }
                         }
                     };
 
@@ -440,7 +440,7 @@ namespace Avalonia.LeakTests
                     Assert.IsType<TabItem>(tabControl.Presenter.Panel.Children[0]);
 
                     // Clear the items and ensure the TabItem is removed.
-                    tabControl.Items = null;
+                    tabControl.ItemsSource = null;
                     window.LayoutManager.ExecuteLayoutPass();
                     Assert.Empty(tabControl.Presenter.Panel.Children);
 
@@ -545,7 +545,7 @@ namespace Avalonia.LeakTests
                 {
                     var contextMenu = new ContextMenu
                     {
-                        Items = new[]
+                        Items =
                         {
                             new MenuItem { Header = "Foo" },
                             new MenuItem { Header = "Foo" },
@@ -594,7 +594,7 @@ namespace Avalonia.LeakTests
                 {
                     var contextMenu = new ContextMenu
                     {
-                        Items = new[]
+                        Items =
                         {
                             new MenuItem { Header = "Foo" },
                             new MenuItem { Header = "Foo" },
@@ -740,7 +740,7 @@ namespace Avalonia.LeakTests
                             }),
                             (lb = new ListBox
                             {
-                                Items = items,
+                                ItemsSource = items,
                                 ItemTemplate = new FuncDataTemplate<int>((_, _) =>
                                     new Canvas
                                     {
@@ -858,7 +858,7 @@ namespace Avalonia.LeakTests
                     // Add the listbox and render it
                     tl.Content = listBox;
                     lm.ExecuteInitialLayoutPass();
-                    listBox.Items = keyGestures;
+                    listBox.ItemsSource = keyGestures;
                     lm.ExecuteLayoutPass();
 
                     // Let the button detach when clearing the source items

tests/Avalonia.Markup.UnitTests/Data/MultiBindingTests.cs

@@ -173,11 +173,11 @@ namespace Avalonia.Markup.UnitTests.Data
                 },
             };
 
-            target.Bind(ItemsControl.ItemsProperty, binding);
+            target.Bind(ItemsControl.ItemsSourceProperty, binding);
             Assert.Equal(target.ItemCount, 3);
-            Assert.Equal(target.Items.ElementAt(0), source.A);
-            Assert.Equal(target.Items.ElementAt(1), source.B);
-            Assert.Equal(target.Items.ElementAt(2), source.C);
+            Assert.Equal(target.ItemsView[0], source.A);
+            Assert.Equal(target.ItemsView[1], source.B);
+            Assert.Equal(target.ItemsView[2], source.C);
         }
 
         private class ConcatConverter : IMultiValueConverter

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs

@@ -122,7 +122,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
         x:DataType='local:TestDataContext'>
-    <ItemsControl Name='itemsControl' Items='{CompiledBinding Path=ListProperty}'>
+    <ItemsControl Name='itemsControl' ItemsSource='{CompiledBinding Path=ListProperty}'>
 	    <ItemsControl.ItemTemplate>
 		    <DataTemplate>
 			    <TextBlock />
@@ -143,7 +143,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
 
                 window.DataContext = dataContext;
 
-                Assert.Equal(dataContext.ListProperty, textBlock.Items);
+                Assert.Equal(dataContext.ListProperty, textBlock.ItemsSource);
             }
         }
         
@@ -528,7 +528,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
         x:DataType='local:TestDataContext'>
-    <ItemsControl Items='{CompiledBinding ListProperty}' Name='target'>
+    <ItemsControl ItemsSource='{CompiledBinding ListProperty}' Name='target'>
         <ItemsControl.ItemTemplate>
             <DataTemplate>
                 <TextBlock Text='{CompiledBinding}' Name='textBlock' />
@@ -1782,7 +1782,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
         x:DataType='local:TestDataContext'
         x:CompileBindings='True'>
-    <ComboBox x:Name='comboBox' Items='{Binding GenericProperty}' SelectedItem='{Binding GenericProperty.CurrentItem}' />
+    <ComboBox x:Name='comboBox' ItemsSource='{Binding GenericProperty}' SelectedItem='{Binding GenericProperty.CurrentItem}' />
 </Window>";
                 var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
                 var comboBox = window.FindControl<ComboBox>("comboBox");

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs

@@ -505,7 +505,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             {
                 var xaml = @"
 <Window xmlns='https://github.com/avaloniaui'>
-    <ItemsControl Name='itemsControl' Items='{Binding}'>
+    <ItemsControl Name='itemsControl' ItemsSource='{Binding}'>
     </ItemsControl>
 </Window>
 ";
@@ -522,7 +522,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
                 target.DataContext = items;
 
-                Assert.Equal(items, itemsControl.Items);
+                Assert.Equal(items, itemsControl.ItemsSource);
             }
         }
 
@@ -760,7 +760,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             {
                 var xaml = @"
 <Window xmlns='https://github.com/avaloniaui'>
-    <ListBox Items='{Binding Items}' SelectedItems='{Binding SelectedItems}'/>
+    <ListBox ItemsSource='{Binding Items}' SelectedItems='{Binding SelectedItems}'/>
 </Window>";
 
                 var window = AvaloniaRuntimeXamlLoader.Parse<Window>(xaml);
@@ -773,7 +773,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
                 window.DataContext = vm;
 
-                Assert.Equal(vm.Items, listBox.Items);
+                Assert.Equal(vm.Items, listBox.ItemsSource);
 
                 Assert.Equal(vm.SelectedItems, listBox.SelectedItems);
             }

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/DataTemplateTests.cs

@@ -74,7 +74,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 <Window xmlns='https://github.com/avaloniaui'
         xmlns:sys='clr-namespace:System;assembly=mscorlib'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
-    <ItemsControl Name='itemsControl' Items='{Binding}'>
+    <ItemsControl Name='itemsControl' ItemsSource='{Binding}'>
         <ItemsControl.ItemTemplate>
             <DataTemplate>
                 <UserControl Name='foo'/>

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs

@@ -377,7 +377,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 };
 
                 var list = window.FindControl<ListBox>("list");
-                list.Items = collection;
+                list.ItemsSource = collection;
 
                 window.Show();
 

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs

@@ -391,7 +391,7 @@ namespace Avalonia.Markup.Xaml.UnitTests
   </ItemsControl>
 </Window>
 ", typeof(XamlIlBugTestsEventHandlerCodeBehind).Assembly, this);
-            ((ItemsControl)Content).Items = new[] {"123"};
+            ((ItemsControl)Content).ItemsSource = new[] {"123"};
         }
     }
     

tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs

@@ -41,7 +41,7 @@ namespace Avalonia.ReactiveUI.UnitTests
                 
                 Content = List;
                 ViewModel = new ExampleViewModel();
-                this.OneWayBind(ViewModel, x => x.Items, x => x.List.Items);
+                this.OneWayBind(ViewModel, x => x.Items, x => x.List.ItemsSource);
             }
         }