diff --git a/src/Avalonia.Controls/ContentControl.cs b/src/Avalonia.Controls/ContentControl.cs
index 6da6da54a5..f9241956bd 100644
--- a/src/Avalonia.Controls/ContentControl.cs
+++ b/src/Avalonia.Controls/ContentControl.cs
@@ -45,6 +45,8 @@ namespace Avalonia.Controls
         static ContentControl()
         {
             ContentControlMixin.Attach<ContentControl>(ContentProperty, x => x.LogicalChildren);
+            PseudoClass(ContentProperty, x => x != null, ":valid");
+            PseudoClass(ContentProperty, x => x == null, ":invalid");
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index c5d3313117..4d229390cb 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -32,24 +32,24 @@ namespace Avalonia.Controls
             ListBoxItem.IsSelectedProperty.AddOwner<TreeViewItem>();
 
         /// <summary>
-        /// Defines the <see cref="Depth"/> property.
+        /// Defines the <see cref="Level"/> property.
         /// </summary>
-        public static readonly DirectProperty<TreeViewItem, int> DepthProperty =
+        public static readonly DirectProperty<TreeViewItem, int> LevelProperty =
             AvaloniaProperty.RegisterDirect<TreeViewItem, int>(
-                nameof(Depth), o => o.Depth);
+                nameof(Level), o => o.Level);
 
         private static readonly ITemplate<IPanel> DefaultPanel =
             new FuncTemplate<IPanel>(() => new StackPanel());
 
         private TreeView _treeView;
         private bool _isExpanded;
-        private int _depth;
+        private int _level;
 
         /// <summary>
         /// Initializes static members of the <see cref="TreeViewItem"/> class.
         /// </summary>
         static TreeViewItem()
-        {            
+        {
             SelectableMixin.Attach<TreeViewItem>(IsSelectedProperty);
             FocusableProperty.OverrideDefaultValue<TreeViewItem>(true);
             ItemsPanelProperty.OverrideDefaultValue<TreeViewItem>(DefaultPanel);
@@ -74,12 +74,12 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets or sets the depth of the item.
+        /// Gets the level/indentation of the item.
         /// </summary>
-        public int Depth
+        public int Level
         {
-            get { return _depth; }
-            private set { SetAndRaise(DepthProperty, ref _depth, value); }
+            get { return _level; }
+            private set { SetAndRaise(LevelProperty, ref _level, value); }
         }
 
         /// <summary>
@@ -106,7 +106,7 @@ namespace Avalonia.Controls
             base.OnAttachedToLogicalTree(e);
             _treeView = this.GetLogicalAncestors().OfType<TreeView>().FirstOrDefault();
 
-            Depth = this.CalculateDistanceFromLogicalParent<TreeView>() - 1;
+            Level = CalculateDistanceFromLogicalParent<TreeView>(this) - 1;
 
             if (ItemTemplate == null && _treeView?.ItemTemplate != null)
             {
@@ -145,5 +145,18 @@ namespace Avalonia.Controls
 
             // Don't call base.OnKeyDown - let events bubble up to containing TreeView.
         }
+
+        private static int CalculateDistanceFromLogicalParent<T>(ILogical logical, int @default = -1) where T : class
+        {
+            var result = 0;
+
+            while (logical != null && logical.GetType() != typeof(T))
+            {
+                ++result;
+                logical = logical.LogicalParent;
+            }
+
+            return logical != null ? result : @default;
+        }
     }
 }
diff --git a/src/Avalonia.Styling/LogicalTree/LogicalExtensions.cs b/src/Avalonia.Styling/LogicalTree/LogicalExtensions.cs
index 47550a876d..276ea6c060 100644
--- a/src/Avalonia.Styling/LogicalTree/LogicalExtensions.cs
+++ b/src/Avalonia.Styling/LogicalTree/LogicalExtensions.cs
@@ -87,20 +87,5 @@ namespace Avalonia.LogicalTree
         {
             return target.GetLogicalAncestors().Any(x => x == logical);
         }
-
-        public static int CalculateDistanceFromLogicalParent<T>(this ILogical logical, int @default = -1) where T : class
-        {
-            Contract.Requires<ArgumentNullException>(logical != null);
-
-            var result = 0;
-
-            while (logical != null && logical.GetType() != typeof(T))
-            {
-                ++result;
-                logical = logical.LogicalParent;
-            }
-
-            return logical != null ? result : @default;
-        }
     }
 }
diff --git a/src/Avalonia.Styling/Styling/PropertyEqualsSelector.cs b/src/Avalonia.Styling/Styling/PropertyEqualsSelector.cs
index 57d5ad9271..25f12ffa57 100644
--- a/src/Avalonia.Styling/Styling/PropertyEqualsSelector.cs
+++ b/src/Avalonia.Styling/Styling/PropertyEqualsSelector.cs
@@ -60,7 +60,7 @@ namespace Avalonia.Styling
 
                 builder.Append(_property.Name);
                 builder.Append('=');
-                builder.Append(_value);
+                builder.Append(_value ?? string.Empty);
                 builder.Append(']');
 
                 _selectorString = builder.ToString();
@@ -78,11 +78,11 @@ namespace Avalonia.Styling
             }
             else if (subscribe)
             {
-                return new SelectorMatch(control.GetObservable(_property).Select(v => Equals(v, _value)));
+                return new SelectorMatch(control.GetObservable(_property).Select(v => Equals(v ?? string.Empty, _value)));
             }
             else
             {
-                return new SelectorMatch(control.GetValue(_property).Equals(_value));
+                return new SelectorMatch((control.GetValue(_property) ?? string.Empty).Equals(_value));
             }
         }
 
diff --git a/src/Avalonia.Themes.Default/Accents/BaseLight.xaml b/src/Avalonia.Themes.Default/Accents/BaseLight.xaml
index 5aac023708..46767feca0 100644
--- a/src/Avalonia.Themes.Default/Accents/BaseLight.xaml
+++ b/src/Avalonia.Themes.Default/Accents/BaseLight.xaml
@@ -1,60 +1,56 @@
 <Style xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=mscorlib">
-  <Style.Resources>
-      
-    <Color x:Key="ThemeAccentColor">#CC119EDA</Color>
-    <Color x:Key="ThemeAccentColor2">#99119EDA</Color>
-    <Color x:Key="ThemeAccentColor3">#66119EDA</Color>
-    <Color x:Key="ThemeAccentColor4">#33119EDA</Color>
-      
-    <Color x:Key="ThemeBackgroundColor">#FFFFFFFF</Color>
-    <Color x:Key="ThemeBorderLightColor">#FFAAAAAA</Color>
-    <Color x:Key="ThemeBorderMidColor">#FF888888</Color>
-    <Color x:Key="ThemeBorderDarkColor">#FF333333</Color>
-    <Color x:Key="ThemeControlLightColor">#FFFFFFFF</Color>
-    <Color x:Key="ThemeControlMidColor">#FFAAAAAA</Color>
-    <Color x:Key="ThemeControlDarkColor">#FF888888</Color>
-    <Color x:Key="ThemeControlHighlightLowColor">#FFF0F0F0</Color>
-    <Color x:Key="ThemeControlHighlightMidColor">#FFD0D0D0</Color>
-    <Color x:Key="ThemeControlHighlightDarkColor">#FF808080</Color>
-    <Color x:Key="ThemeForegroundColor">#FF000000</Color>
-    <Color x:Key="ThemeForegroundLightColor">#FF808080</Color>
-      
-    <Color x:Key="HighlightColor">#FF086F9E</Color>
-    <Color x:Key="ErrorColor">#FFFF0000</Color>
-    <Color x:Key="ErrorLightColor">#10FF0000</Color>
+    <Style.Resources>
 
-    <Color x:Key="InvisibleSelectionColor">#01000000</Color>
+        <Color x:Key="ThemeAccentColor">#CC119EDA</Color>
+        <Color x:Key="ThemeAccentColor2">#99119EDA</Color>
+        <Color x:Key="ThemeAccentColor3">#66119EDA</Color>
+        <Color x:Key="ThemeAccentColor4">#33119EDA</Color>
 
-    <SolidColorBrush x:Key="ThemeBackgroundBrush" Color="{DynamicResource ThemeBackgroundColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeBorderLightBrush" Color="{DynamicResource ThemeBorderLightColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeBorderMidBrush" Color="{DynamicResource ThemeBorderMidColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeBorderDarkBrush" Color="{DynamicResource ThemeBorderDarkColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlLightBrush" Color="{DynamicResource ThemeControlLightColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlMidBrush" Color="{DynamicResource ThemeControlMidColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlDarkBrush" Color="{DynamicResource ThemeControlDarkColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlHighlightLowBrush" Color="{DynamicResource ThemeControlHighlightLowColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlHighlightMidBrush" Color="{DynamicResource ThemeControlHighlightMidColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeControlHighlightDarkBrush" Color="{DynamicResource ThemeControlHighlightDarkColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeForegroundBrush" Color="{DynamicResource ThemeForegroundColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeForegroundLightBrush" Color="{DynamicResource ThemeForegroundLightColor}"></SolidColorBrush>
-      
-    <SolidColorBrush x:Key="HighlightBrush" Color="{DynamicResource HighlightColor}"></SolidColorBrush>    
-    <SolidColorBrush x:Key="ThemeAccentBrush" Color="{DynamicResource ThemeAccentColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeAccentBrush2" Color="{DynamicResource ThemeAccentColor2}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeAccentBrush3" Color="{DynamicResource ThemeAccentColor3}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ThemeAccentBrush4" Color="{DynamicResource ThemeAccentColor4}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ErrorBrush" Color="{DynamicResource ErrorColor}"></SolidColorBrush>
-    <SolidColorBrush x:Key="ErrorLightBrush" Color="{DynamicResource ErrorLightColor}"></SolidColorBrush>
-    
-    <SolidColorBrush x:Key="InvisibleSelectionBrush" Color="{DynamicResource InvisibleSelectionColor}"></SolidColorBrush>
-      
-    <Thickness x:Key="ThemeBorderThickness">2</Thickness>
-    <sys:Double x:Key="ThemeDisabledOpacity">0.5</sys:Double>
+        <Color x:Key="ThemeBackgroundColor">#FFFFFFFF</Color>
+        <Color x:Key="ThemeBorderLightColor">#FFAAAAAA</Color>
+        <Color x:Key="ThemeBorderMidColor">#FF888888</Color>
+        <Color x:Key="ThemeBorderDarkColor">#FF333333</Color>
+        <Color x:Key="ThemeControlLightColor">#FFFFFFFF</Color>
+        <Color x:Key="ThemeControlMidColor">#FFAAAAAA</Color>
+        <Color x:Key="ThemeControlDarkColor">#FF888888</Color>
+        <Color x:Key="ThemeControlHighlightLowColor">#FFF0F0F0</Color>
+        <Color x:Key="ThemeControlHighlightMidColor">#FFD0D0D0</Color>
+        <Color x:Key="ThemeControlHighlightDarkColor">#FF808080</Color>
+        <Color x:Key="ThemeForegroundColor">#FF000000</Color>
+        <Color x:Key="ThemeForegroundLightColor">#FF808080</Color>
 
-    <sys:Double x:Key="FontSizeSmall">10</sys:Double>
-    <sys:Double x:Key="FontSizeNormal">12</sys:Double>
-    <sys:Double x:Key="FontSizeLarge">16</sys:Double>
-  </Style.Resources>
+        <Color x:Key="HighlightColor">#FF086F9E</Color>
+        <Color x:Key="ErrorColor">#FFFF0000</Color>
+        <Color x:Key="ErrorLightColor">#10FF0000</Color>
+
+        <SolidColorBrush x:Key="ThemeBackgroundBrush" Color="{DynamicResource ThemeBackgroundColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeBorderLightBrush" Color="{DynamicResource ThemeBorderLightColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeBorderMidBrush" Color="{DynamicResource ThemeBorderMidColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeBorderDarkBrush" Color="{DynamicResource ThemeBorderDarkColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlLightBrush" Color="{DynamicResource ThemeControlLightColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlMidBrush" Color="{DynamicResource ThemeControlMidColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlDarkBrush" Color="{DynamicResource ThemeControlDarkColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlHighlightLowBrush" Color="{DynamicResource ThemeControlHighlightLowColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlHighlightMidBrush" Color="{DynamicResource ThemeControlHighlightMidColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeControlHighlightDarkBrush" Color="{DynamicResource ThemeControlHighlightDarkColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeForegroundBrush" Color="{DynamicResource ThemeForegroundColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeForegroundLightBrush" Color="{DynamicResource ThemeForegroundLightColor}"></SolidColorBrush>
+
+        <SolidColorBrush x:Key="HighlightBrush" Color="{DynamicResource HighlightColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeAccentBrush" Color="{DynamicResource ThemeAccentColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeAccentBrush2" Color="{DynamicResource ThemeAccentColor2}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeAccentBrush3" Color="{DynamicResource ThemeAccentColor3}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ThemeAccentBrush4" Color="{DynamicResource ThemeAccentColor4}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ErrorBrush" Color="{DynamicResource ErrorColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="ErrorLightBrush" Color="{DynamicResource ErrorLightColor}"></SolidColorBrush>
+
+        <Thickness x:Key="ThemeBorderThickness">2</Thickness>
+        <sys:Double x:Key="ThemeDisabledOpacity">0.5</sys:Double>
+
+        <sys:Double x:Key="FontSizeSmall">10</sys:Double>
+        <sys:Double x:Key="FontSizeNormal">12</sys:Double>
+        <sys:Double x:Key="FontSizeLarge">16</sys:Double>
+    </Style.Resources>
 </Style>
diff --git a/src/Avalonia.Themes.Default/CheckBox.xaml b/src/Avalonia.Themes.Default/CheckBox.xaml
index 62a05a3525..3d14dd8e51 100644
--- a/src/Avalonia.Themes.Default/CheckBox.xaml
+++ b/src/Avalonia.Themes.Default/CheckBox.xaml
@@ -40,6 +40,9 @@
       </ControlTemplate>
     </Setter>
   </Style>
+  <Style Selector="CheckBox:invalid /template/ ContentPresenter#PART_ContentPresenter">
+    <Setter Property="IsVisible" Value="False"/>
+  </Style>
   <Style Selector="CheckBox:pointerover /template/ Border#border">
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeBorderDarkBrush}"/>
   </Style>
@@ -58,4 +61,4 @@
   <Style Selector="CheckBox:disabled /template/ Border#border">
     <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}"/>
   </Style>
-</Styles>
\ No newline at end of file
+</Styles>
diff --git a/src/Avalonia.Themes.Default/TreeViewItem.xaml b/src/Avalonia.Themes.Default/TreeViewItem.xaml
index ada86d3535..b5e0e7a005 100644
--- a/src/Avalonia.Themes.Default/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Default/TreeViewItem.xaml
@@ -1,92 +1,92 @@
 <Styles xmlns="https://github.com/avaloniaui"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:converters="clr-namespace:Avalonia.Controls.Converters;assembly=Avalonia.Controls">
-  <Style Selector="TreeViewItem">
-    <Style.Resources>
-      <converters:MarginMultiplierConverter Indent="16" Left="True" x:Key="LeftMarginConverter" />
-    </Style.Resources>
-    <Setter Property="Padding" Value="2"/>
-    <Setter Property="Background" Value="{DynamicResource InvisibleSelectionBrush}"/>
-    <Setter Property="Template">
-      <ControlTemplate>
-        <StackPanel>
-          <Border Name="SelectionBorder"
-                  Focusable="True"
-                  Background="{TemplateBinding Background}"
-                  BorderBrush="{TemplateBinding BorderBrush}"
-                  BorderThickness="{TemplateBinding BorderThickness}"
-                  TemplatedControl.IsTemplateFocusTarget="True">
-            <Grid ColumnDefinitions="16, *" 
-                  Margin="{TemplateBinding Depth, Mode=OneWay, Converter={StaticResource LeftMarginConverter}}" >
-              <ToggleButton Name="expander"
-                            Focusable="False"
-                            IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}"/>
-              <ContentPresenter Name="PART_HeaderPresenter"
-                                Focusable="False"
-                                Content="{TemplateBinding Header}"
-                                HorizontalContentAlignment="{TemplateBinding HorizontalAlignment}"
-                                Padding="{TemplateBinding Padding}"
-                                Grid.Column="1"/>
-            </Grid>
-          </Border>
-          <ItemsPresenter Name="PART_ItemsPresenter"
-                          IsVisible="{TemplateBinding IsExpanded}"
-                          Items="{TemplateBinding Items}"
-                          ItemsPanel="{TemplateBinding ItemsPanel}"
-                          MemberSelector="{TemplateBinding MemberSelector}"/>
-        </StackPanel>
-      </ControlTemplate>
-    </Setter>
-  </Style>
+    <Style Selector="TreeViewItem">
+        <Style.Resources>
+            <converters:MarginMultiplierConverter Indent="16" Left="True" x:Key="LeftMarginConverter" />
+        </Style.Resources>
+        <Setter Property="Padding" Value="2"/>
+        <Setter Property="Background" Value="Transparent"/>
+        <Setter Property="Template">
+            <ControlTemplate>
+                <StackPanel>
+                    <Border Name="SelectionBorder"
+                            Focusable="True"
+                            Background="{TemplateBinding Background}"
+                            BorderBrush="{TemplateBinding BorderBrush}"
+                            BorderThickness="{TemplateBinding BorderThickness}"
+                            TemplatedControl.IsTemplateFocusTarget="True">
+                        <Grid ColumnDefinitions="16, *"
+                              Margin="{TemplateBinding Level, Mode=OneWay, Converter={StaticResource LeftMarginConverter}}" >
+                            <ToggleButton Name="expander"
+                                          Focusable="False"
+                                          IsChecked="{TemplateBinding IsExpanded, Mode=TwoWay}"/>
+                            <ContentPresenter Name="PART_HeaderPresenter"
+                                              Focusable="False"
+                                              Content="{TemplateBinding Header}"
+                                              HorizontalContentAlignment="{TemplateBinding HorizontalAlignment}"
+                                              Padding="{TemplateBinding Padding}"
+                                              Grid.Column="1"/>
+                        </Grid>
+                    </Border>
+                    <ItemsPresenter Name="PART_ItemsPresenter"
+                                    IsVisible="{TemplateBinding IsExpanded}"
+                                    Items="{TemplateBinding Items}"
+                                    ItemsPanel="{TemplateBinding ItemsPanel}"
+                                    MemberSelector="{TemplateBinding MemberSelector}"/>
+                </StackPanel>
+            </ControlTemplate>
+        </Setter>
+    </Style>
 
-  <Style Selector="TreeViewItem /template/ ToggleButton#expander">
-    <Setter Property="Template">
-      <ControlTemplate>
-        <Border Background="Transparent"
-                Width="14"
-                Height="12"
-                HorizontalAlignment="Center"
-                VerticalAlignment="Center">
-          <Path Fill="{DynamicResource ThemeForegroundBrush}"
-                HorizontalAlignment="Center"
-                VerticalAlignment="Center"
-                Data="M 0 2 L 4 6 L 0 10 Z"/>
-        </Border>
-      </ControlTemplate>
-    </Setter>
-  </Style>
+    <Style Selector="TreeViewItem /template/ ToggleButton#expander">
+        <Setter Property="Template">
+            <ControlTemplate>
+                <Border Background="Transparent"
+                        Width="14"
+                        Height="12"
+                        HorizontalAlignment="Center"
+                        VerticalAlignment="Center">
+                    <Path Fill="{DynamicResource ThemeForegroundBrush}"
+                          HorizontalAlignment="Center"
+                          VerticalAlignment="Center"
+                          Data="M 0 2 L 4 6 L 0 10 Z"/>
+                </Border>
+            </ControlTemplate>
+        </Setter>
+    </Style>
 
-  <Style Selector="TreeViewItem /template/ ContentPresenter#PART_HeaderPresenter">
-    <Setter Property="Padding" Value="2"/>
-  </Style>
+    <Style Selector="TreeViewItem /template/ ContentPresenter#PART_HeaderPresenter">
+        <Setter Property="Padding" Value="2"/>
+    </Style>
 
-  <Style Selector="TreeViewItem[IsSelected=false] /template/ Border#SelectionBorder[IsPointerOver=true]">
-    <Setter Property="Background" Value="{DynamicResource ThemeControlHighlightMidBrush}"/>
-  </Style>
+    <Style Selector="TreeViewItem /template/ Border#SelectionBorder:pointerover">
+        <Setter Property="Background" Value="{DynamicResource ThemeControlHighlightMidBrush}"/>
+    </Style>
 
-  <Style Selector="TreeViewItem[IsSelected=true] /template/ Border#SelectionBorder">
-    <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush4}"/>
-  </Style>
+    <Style Selector="TreeViewItem:selected /template/ Border#SelectionBorder">
+        <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush4}"/>
+    </Style>
 
-  <Style Selector="TreeViewItem[IsSelected=true] /template/ Border#SelectionBorder[IsPointerOver=false][IsFocused=true]">
-    <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
-  </Style>
+    <Style Selector="TreeViewItem:selected /template/ Border#SelectionBorder:focus">
+        <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
+    </Style>
 
-  <Style Selector="TreeViewItem[IsSelected=true] /template/ Border#SelectionBorder[IsPointerOver=true][IsFocused=false]">
-    <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
-  </Style>
+    <Style Selector="TreeViewItem:selected /template/ Border#SelectionBorder:pointerover">
+        <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
+    </Style>
 
-  <Style Selector="TreeViewItem[IsSelected=true] /template/ Border#SelectionBorder[IsPointerOver=true][IsFocused=true]">
-    <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush2}"/>
-  </Style>
+    <Style Selector="TreeViewItem:selected /template/ Border#SelectionBorder:pointerover:focus">
+        <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush2}"/>
+    </Style>
 
-  <Style Selector="TreeViewItem /template/ ToggleButton#expander:checked">
-    <Setter Property="RenderTransform">
-      <RotateTransform Angle="45"/>
-    </Setter>
-  </Style>
+    <Style Selector="TreeViewItem /template/ ToggleButton#expander:checked">
+        <Setter Property="RenderTransform">
+            <RotateTransform Angle="45"/>
+        </Setter>
+    </Style>
 
-  <Style Selector="TreeViewItem:empty /template/ ToggleButton#expander">
-    <Setter Property="IsVisible" Value="False"/>
-  </Style>
+    <Style Selector="TreeViewItem:empty /template/ ToggleButton#expander">
+        <Setter Property="IsVisible" Value="False"/>
+    </Style>
 </Styles>