DataGridComboBoxColumn

samples/ControlCatalog/Models/Person.cs

@@ -16,6 +16,7 @@ namespace ControlCatalog.Models
         string _firstName;
         string _lastName;
         bool _isBanned;
+        UserRole _role;
 
         public string FirstName
         {
@@ -55,7 +56,18 @@ namespace ControlCatalog.Models
             {
                 _isBanned = value;
 
-                OnPropertyChanged(nameof(_isBanned));
+                OnPropertyChanged(nameof(IsBanned));
+            }
+        }
+
+        public UserRole Role
+        {
+            get => _role;
+            set
+            {
+                _role = value;
+
+                OnPropertyChanged(nameof(Role));
             }
         }
 
@@ -107,4 +119,11 @@ namespace ControlCatalog.Models
                 return null;
         }
     }
+
+    public enum UserRole
+    {
+        Guest,
+        User,
+        Admin
+    }
 }

samples/ControlCatalog/Pages/DataGridPage.xaml

@@ -1,6 +1,7 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:local="clr-namespace:ControlCatalog.Models;assembly=ControlCatalog"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:col="using:System.Collections"
              x:Class="ControlCatalog.Pages.DataGridPage">
   <UserControl.Resources>
     <local:GDPValueConverter x:Key="GDPConverter" />
@@ -51,6 +52,15 @@
               <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridTextColumn Header="Last" Binding="{Binding LastName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridCheckBoxColumn Header="Is Banned" Binding="{Binding IsBanned}" Width="*" IsThreeState="{Binding #IsThreeStateCheckBox.IsChecked, Mode=OneWay}" />
+              <DataGridComboBoxColumn Header="Role" Binding="{Binding Role}">
+                <DataGridComboBoxColumn.Items>
+                  <col:ArrayList>
+                    <local:UserRole>Guest</local:UserRole>
+                    <local:UserRole>User</local:UserRole>
+                    <local:UserRole>Admin</local:UserRole>
+                  </col:ArrayList>
+                </DataGridComboBoxColumn.Items>
+              </DataGridComboBoxColumn>
             </DataGrid.Columns>
           </DataGrid>
           <Button Grid.Row="1" Name="btnAdd" Margin="12,0,12,12" Content="Add" HorizontalAlignment="Right" />

src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs

@@ -131,7 +131,7 @@ namespace Avalonia.Controls
 
         protected abstract IControl GenerateEditingElementDirect(DataGridCell cell, object dataItem); 
 
-        internal AvaloniaProperty BindingTarget { get; set; } 
+        internal AvaloniaProperty BindingTarget { get; set; }
 
         internal void SetHeaderFromBinding()
         {

src/Avalonia.Controls.DataGrid/DataGridComboBoxColumn.cs

@@ -0,0 +1,312 @@
+using Avalonia.Interactivity;
+using Avalonia.Media;
+using System;
+using System.ComponentModel;
+using Avalonia.Layout;
+using Avalonia.Markup.Xaml.MarkupExtensions;
+using Avalonia.Data;
+using Avalonia.Controls.Utils;
+using Avalonia.Data.Core;
+using System.Collections;
+using System.Linq;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Represents a <see cref="DataGrid"/> column that hosts textual content in its cells. In edit mode data can be changed to a value from a collection hosted in a ComboBox.
+    /// </summary>
+    public class DataGridComboBoxColumn : DataGridBoundColumn
+    {
+        private const string DATAGRID_TextColumnCellTextBlockMarginKey = "DataGridTextColumnCellTextBlockMargin";
+
+        private double? _fontSize;
+        private DataGrid _owningGrid;
+        private FontStyle? _fontStyle;
+        private FontWeight? _fontWeight;
+        private Brush _foreground;
+        private IEnumerable items;
+
+        public DataGridComboBoxColumn()
+        {
+            BindingTarget = ComboBox.SelectedItemProperty;
+        }
+
+        /// <summary>
+        /// Identifies the ItemsSource dependency property.
+        /// </summary>
+        public static readonly DirectProperty<DataGridComboBoxColumn, IEnumerable> ItemsProperty =
+            ItemsControl.ItemsProperty.AddOwner<DataGridComboBoxColumn>(o => o.Items, (o, v) => o.Items = v);
+
+        /// <summary>
+        /// Gets or sets a collection that is used to generate the content of the ComboBox while in editing mode.
+        /// </summary>
+        public IEnumerable Items
+        {
+            get => items;
+            set => SetAndRaise(ItemsProperty, ref items, value);
+        }
+
+        /// <summary>
+        /// Identifies the FontFamily dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<FontFamily> FontFamilyProperty =
+            TextBlock.FontFamilyProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets the font name.
+        /// </summary>
+        public FontFamily FontFamily
+        {
+            get => GetValue(FontFamilyProperty);
+            set => SetValue(FontFamilyProperty, value);
+        }
+
+        /// <summary>
+        /// Identifies the FontSize dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<double> FontSizeProperty =
+            TextBlock.FontSizeProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets the font size.
+        /// </summary>
+        // Use DefaultValue here so undo in the Designer will set this to NaN
+        [DefaultValue(double.NaN)]
+        public double FontSize
+        {
+            get => GetValue(FontSizeProperty);
+            set => SetValue(FontSizeProperty, value);
+        }
+
+        /// <summary>
+        /// Identifies the FontStyle dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<FontStyle> FontStyleProperty =
+            TextBlock.FontStyleProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets the font style.
+        /// </summary>
+        public FontStyle FontStyle
+        {
+            get => GetValue(FontStyleProperty);
+            set => SetValue(FontStyleProperty, value);
+        }
+
+        /// <summary>
+        /// Identifies the FontWeight dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<FontWeight> FontWeightProperty =
+            TextBlock.FontWeightProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets the font weight or thickness.
+        /// </summary>
+        public FontWeight FontWeight
+        {
+            get => GetValue(FontWeightProperty);
+            set => SetValue(FontWeightProperty, value);
+        }
+
+        /// <summary>
+        /// Identifies the Foreground dependency property.
+        /// </summary>
+        public static readonly AttachedProperty<IBrush> ForegroundProperty =
+            TextBlock.ForegroundProperty.AddOwner<DataGridTextColumn>();
+
+        /// <summary>
+        /// Gets or sets a brush that describes the foreground of the column cells.
+        /// </summary>
+        public IBrush Foreground
+        {
+            get => GetValue(ForegroundProperty);
+            set => SetValue(ForegroundProperty, value);
+        }
+
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == FontFamilyProperty
+                || change.Property == FontSizeProperty
+                || change.Property == FontStyleProperty
+                || change.Property == FontWeightProperty
+                || change.Property == ForegroundProperty
+                || change.Property == ItemsProperty)
+            {
+                NotifyPropertyChanged(change.Property.Name);
+            }
+        }
+
+        /// <summary>
+        /// Gets a <see cref="T:Windows.UI.Xaml.Controls.ComboBox"/> control that is bound to the column's ItemsSource collection.
+        /// </summary>
+        /// <param name="cell">The cell that will contain the generated element.</param>
+        /// <param name="dataItem">The data item represented by the row that contains the intended cell.</param>
+        /// <returns>A new <see cref="T:Windows.UI.Xaml.Controls.ComboBox"/> control that is bound to the column's ItemsSource collection.</returns>
+        protected override IControl GenerateEditingElementDirect(DataGridCell cell, object dataItem)
+        {
+            EnsureColumnBinding(dataItem);
+
+            var comboBox = new ComboBox
+            {
+                Margin = new Thickness(),
+                HorizontalAlignment = HorizontalAlignment.Stretch,
+                VerticalAlignment = VerticalAlignment.Center,
+                DataContext = dataItem
+            };
+
+            SyncProperties(comboBox);
+            
+            return comboBox;
+        }
+
+        /// <summary>
+        /// Gets a read-only <see cref="TextBlock"/> element that is bound to the column's <see cref="DataGridBoundColumn.Binding"/> property value.
+        /// </summary>
+        /// <param name="cell">The cell that will contain the generated element.</param>
+        /// <param name="dataItem">The data item represented by the row that contains the intended cell.</param>
+        /// <returns>A new, read-only <see cref="TextBlock"/> element that is bound to the column's <see cref="DataGridBoundColumn.Binding"/> property value.</returns>
+        protected override IControl GenerateElement(DataGridCell cell, object dataItem)
+        {
+            EnsureColumnBinding(dataItem);
+
+            var textBlockElement = new TextBlock
+            {
+                [!Layoutable.MarginProperty] = new DynamicResourceExtension(DATAGRID_TextColumnCellTextBlockMarginKey),
+                VerticalAlignment = VerticalAlignment.Center,
+                [!TextBlock.TextProperty] = Binding
+            };
+
+            SyncProperties(textBlockElement);
+
+            if (Binding != null)
+            {
+                textBlockElement.Text = dataItem.ToString();
+            }
+
+            return textBlockElement;
+        }
+
+        /// <summary>
+        /// Causes the column cell being edited to revert to the specified value.
+        /// </summary>
+        /// <param name="editingElement">The element that the column displays for a cell in editing mode.</param>
+        /// <param name="uneditedValue">The previous, unedited value in the cell being edited.</param>
+        protected override void CancelCellEdit(IControl editingElement, object uneditedValue)
+        {
+            if (editingElement is ComboBox comboBox)
+            {
+                if (uneditedValue != null)
+                {
+                    var property = uneditedValue.GetType().GetNestedProperty(Binding.GetBindingPropertyName());
+
+                    if (property == null)
+                    {
+                        comboBox.SelectedItem = uneditedValue;
+                    }
+                    else
+                    {
+                        var value = TypeHelper.GetNestedPropertyValue(uneditedValue, Binding.GetBindingPropertyName());
+                        var selection = Items?.Cast<object>().FirstOrDefault(x => TypeHelper.GetNestedPropertyValue(x, Binding.GetBindingPropertyName()).Equals(value));
+
+                        comboBox.SelectedItem = selection;
+                    }
+                }
+                else
+                {
+                    comboBox.SelectedItem = null;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Called when the cell in the column enters editing mode.
+        /// </summary>
+        /// <param name="editingElement">The element that the column displays for a cell in editing mode.</param>
+        /// <param name="editingEventArgs">Information about the user gesture that is causing a cell to enter editing mode.</param>
+        /// <returns>The unedited value. </returns>
+        protected override object PrepareCellForEdit(IControl editingElement, RoutedEventArgs editingEventArgs)
+        {
+            return (editingElement as ComboBox)?.SelectedItem;
+        }
+
+        /// <summary>
+        /// Called by the DataGrid control when this column asks for its elements to be updated, because a property changed.
+        /// </summary>
+        protected internal override void RefreshCellContent(IControl element, string propertyName)
+        {
+            if (element == null)
+            {
+                throw new ArgumentNullException(nameof(element));
+            }
+
+            if (element is AvaloniaObject content)
+            {
+                if (propertyName == nameof(FontFamily))
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, FontFamilyProperty);
+                }
+                else if (propertyName == nameof(FontSize))
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, FontSizeProperty);
+                }
+                else if (propertyName == nameof(FontStyle))
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, FontStyleProperty);
+                }
+                else if (propertyName == nameof(FontWeight))
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, FontWeightProperty);
+                }
+                else if (propertyName == nameof(Foreground))
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, ForegroundProperty);
+                }
+                if (propertyName == nameof(Items)
+                    && content is ComboBox)
+                {
+                    DataGridHelper.SyncColumnProperty(this, content, ItemsProperty);
+                }
+            }
+            else
+            {
+                throw DataGridError.DataGrid.ValueIsNotAnInstanceOf("element", typeof(AvaloniaObject));
+            }
+        }
+
+        private void SyncProperties(AvaloniaObject content)
+        {
+            DataGridHelper.SyncColumnProperty(this, content, FontFamilyProperty);
+            DataGridHelper.SyncColumnProperty(this, content, FontSizeProperty);
+            DataGridHelper.SyncColumnProperty(this, content, FontStyleProperty);
+            DataGridHelper.SyncColumnProperty(this, content, FontWeightProperty);
+            DataGridHelper.SyncColumnProperty(this, content, ForegroundProperty);
+            if (content is ComboBox)
+            {
+                DataGridHelper.SyncColumnProperty(this, content, ItemsProperty);
+            }
+        }
+
+        private void EnsureColumnBinding(object dataItem)
+        {
+            var path = (Binding as Binding)?.Path ?? (Binding as CompiledBindingExtension)?.Path.ToString();
+            if (path == null)
+            {
+                if (!string.IsNullOrEmpty(Header as string))
+                {
+                    throw DataGridError.DataGridComboBoxColumn.UnsetBinding(Header as string);
+                }
+
+                throw DataGridError.DataGridComboBoxColumn.UnsetBinding(GetType());
+            }
+
+            var property = dataItem?.GetType().GetNestedProperty(path);
+
+            if (property == null && dataItem != null)
+            {
+                throw DataGridError.DataGridComboBoxColumn.UnknownBindingPath(Binding, dataItem?.GetType());
+            }
+        }
+    }
+}

src/Avalonia.Controls.DataGrid/DataGridError.cs

@@ -6,6 +6,10 @@
 using System;
 using System.Globalization;
 
+using Avalonia.Data;
+using Avalonia.Markup.Xaml.MarkupExtensions;
+using Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings;
+
 namespace Avalonia.Controls
 {
 
@@ -174,6 +178,41 @@ namespace Avalonia.Controls
             }
         }
 
+        public static class DataGridComboBoxColumn
+        {
+            public static ArgumentException UnsetBinding(string header)
+            {
+                return new ArgumentException(Format("Binding for column {0} is null. Ensure that the binding path has been set correctly.", header));
+            }
+
+            public static ArgumentException UnsetBinding(Type type)
+            {
+                return new ArgumentException(Format("Binding for column of type {0} is null. Ensure that the binding path has been set correctly.", type.FullName));
+            }
+
+            public static ArgumentException UnknownBindingPath(IBinding binding, Type type)
+            {
+                var path = (binding as Binding)?.Path ?? (binding as CompiledBindingExtension)?.Path.ToString();
+                return new ArgumentException(Format("Binding path {0} could not be found in type {1}. Ensure that the binding path has been set correctly.", path, type.FullName));
+            }
+
+            public static ArgumentException UnknownDisplayMemberPath(string displayMemberPath, Type type)
+            {
+                return new ArgumentException(Format("DisplayMemberPath {0} could not be found in type {1}. Ensure that the value has been set correctly and note that for built-in types DisplayMemberPath should not be used.", displayMemberPath, type.FullName));
+            }
+
+            public static ArgumentException UnknownItemsSourcePath(IBinding binding)
+            {
+                var path = (binding as Binding)?.Path ?? (binding as CompiledBindingExtension)?.Path.ToString();
+                return new ArgumentException(Format("The Items elements do not contain a property {0}. Ensure that the binding path has been set correctly.", path));
+            }
+
+            public static ArgumentException BindingTypeMismatch(Type bindingType, Type itemSourceType)
+            {
+                return new ArgumentException(Format("The DataGridComboBoxColumn ItemSource elements of type \'{0}\' do not match the Binding type \'{1}\'. Ensure that the paths have been set correctly and specify a DisplayMemberPath for non built-in types.", itemSourceType.FullName, bindingType.FullName));
+            }
+        }
+
         public static class DataGridTemplateColumn
         {
             public static TypeInitializationException MissingTemplateForType(Type type)
@@ -187,4 +226,4 @@ namespace Avalonia.Controls
             return String.Format(CultureInfo.CurrentCulture, formatString, args);
         }
     }
-}
+}

src/Avalonia.Controls.DataGrid/Utils/ReflectionHelper.cs

@@ -10,8 +10,12 @@ using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Diagnostics;
 using System.Globalization;
+using System.Linq;
 using System.Reflection;
 
+using Avalonia.Data;
+using Avalonia.Markup.Xaml.MarkupExtensions;
+
 namespace Avalonia.Controls.Utils
 {
     internal static class TypeHelper
@@ -239,6 +243,12 @@ namespace Avalonia.Controls.Utils
             return s;
         }
 
+        internal static string GetBindingPropertyName(this IBinding binding)
+        {
+            var path = (binding as Binding)?.Path ?? (binding as CompiledBindingExtension)?.Path.ToString();
+            return path?.Split('.')?.LastOrDefault();
+        }
+
         internal static Type GetNestedPropertyType(this Type parentType, string propertyPath)
         {
             if (parentType == null || String.IsNullOrEmpty(propertyPath))