feat: selected item is now two-way binding by default.

demo/Ursa.Demo/Pages/TreeComboBoxDemo.axaml

@@ -31,17 +31,22 @@
         <u:TreeComboBox
             Width="300"
             HorizontalAlignment="Left"
+            SelectedItem="{Binding SelectedItem}"
             ItemsSource="{Binding Items}">
             <u:TreeComboBox.ItemTemplate>
                 <TreeDataTemplate ItemsSource="{Binding Children}">
                     <TextBlock Text="{Binding ItemName}" />
                 </TreeDataTemplate>
             </u:TreeComboBox.ItemTemplate>
-            <u:TreeComboBox.SelectedItemTemplate>
-                <DataTemplate>
-                    <TextBlock Text="{Binding ItemName}" />
-                </DataTemplate>
-            </u:TreeComboBox.SelectedItemTemplate>
         </u:TreeComboBox>
+        
+        <ContentControl Content="{Binding SelectedItem}">
+            <ContentControl.ContentTemplate>
+                <DataTemplate DataType="vm:TreeComboBoxItemViewModel">
+                    <TextBlock Text="{Binding ItemName}"></TextBlock>
+                </DataTemplate>
+            </ContentControl.ContentTemplate>
+        </ContentControl>
+        
     </StackPanel>
 </UserControl>

demo/Ursa.Demo/ViewModels/TreeComboBoxDemoViewModel.cs

@@ -3,8 +3,9 @@ using CommunityToolkit.Mvvm.ComponentModel;
 
 namespace Ursa.Demo.ViewModels;
 
-public class TreeComboBoxDemoViewModel: ObservableObject
+public partial class TreeComboBoxDemoViewModel: ObservableObject
 {
+    [ObservableProperty] private TreeComboBoxItemViewModel? _selectedItem;
     public List<TreeComboBoxItemViewModel> Items { get; set; }
 
     public TreeComboBoxDemoViewModel()

src/Ursa.Themes.Semi/Controls/TreeComboBox.axaml

@@ -2,10 +2,12 @@
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:u="https://irihi.tech/ursa"
                     xmlns:iri="https://irihi.tech/shared"
-                    xmlns:converters="clr-namespace:Avalonia.Controls.Converters;assembly=Avalonia.Controls">
+                    xmlns:converters="clr-namespace:Avalonia.Controls.Converters;assembly=Avalonia.Controls"
+                    xmlns:converters1="clr-namespace:Ursa.Themes.Semi.Converters">
     <!-- Add Resources Here -->
     
     <converters:MarginMultiplierConverter x:Key="LeftMarginConverter" Indent="20" Left="True"/>
+    <converters1:SelectedItemTemplateConverter x:Key="SelectedItemTemplateConverter"/>
     
     <ControlTheme x:Key="{x:Type u:TreeComboBox}" TargetType="u:TreeComboBox">
         <Setter Property="Padding" Value="{DynamicResource ComboBoxSelectorDefaultPadding}"/>
@@ -17,7 +19,7 @@
         <Setter Property="Cursor" Value="Hand"/>
         <Setter Property="Template">
             <ControlTemplate TargetType="u:TreeComboBox">
-                <Grid ColumnDefinitions="*, Auto, 32">
+                <Grid ColumnDefinitions="*, Auto, Auto">
                     <Border Grid.Column="0" 
                             Name="Background"
                             Grid.ColumnSpan="3" 
@@ -44,8 +46,14 @@
                         Margin="{TemplateBinding Padding}"
                         VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                         VerticalAlignment="Center"
-                        ContentTemplate="{TemplateBinding SelectedItemTemplate}"
+                        Content="{TemplateBinding SelectionBoxItem}">
-                        Content="{TemplateBinding SelectionBoxItem}"/>
+                        <ContentPresenter.ContentTemplate>
+                            <MultiBinding Converter="{x:Static converters1:SelectedItemTemplateConverter.Instance}">
+                                <TemplateBinding Property="SelectedItemTemplate"/>
+                                <TemplateBinding  Property="ItemTemplate"/>
+                            </MultiBinding>
+                        </ContentPresenter.ContentTemplate>
+                    </ContentPresenter>
                     <Border
                         x:Name="DropDownOverlay"
                         Grid.Column="2"
@@ -54,19 +62,18 @@
                         HorizontalAlignment="Right"
                         Background="Transparent"
                         IsVisible="False" />
-
+                    <Panel Grid.Column="2" Width="32" IsHitTestVisible="False">
-                    <PathIcon
+                        <PathIcon
-                        x:Name="DropDownGlyph"
+                            x:Name="DropDownGlyph"
-                        Grid.Column="2"
+                            Width="12"
-                        Width="12"
+                            Height="12"
-                        Height="12"
+                            Margin="0,0,10,0"
-                        Margin="0,0,10,0"
+                            HorizontalAlignment="Right"
-                        HorizontalAlignment="Right"
+                            VerticalAlignment="Center"
-                        VerticalAlignment="Center"
+                            Data="{DynamicResource ComboBoxIcon}"
-                        Data="{DynamicResource ComboBoxIcon}"
+                            Foreground="{DynamicResource ComboBoxIconDefaultForeground}"
-                        Foreground="{DynamicResource ComboBoxIconDefaultForeground}"
+                            UseLayoutRounding="False" />
-                        IsHitTestVisible="False"
+                    </Panel>
-                        UseLayoutRounding="False" />
                     <Popup 
                         Name="{x:Static iri:PartNames.PART_Popup}" 
                         Grid.Column="0" 
@@ -77,7 +84,7 @@
                         PlacementTarget="Background"
                         WindowManagerAddShadowHint="False"
                         IsLightDismissEnabled="True" 
-                        IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}}">
+                        IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}">
                         <Border 
                             Name="PopupBorder" 
                             Margin="0 4" 

src/Ursa.Themes.Semi/Converters/SelectedItemTemplateConverter.cs

@@ -0,0 +1,24 @@
+using System.Globalization;
+using Avalonia;
+using Avalonia.Controls.Templates;
+using Avalonia.Data.Converters;
+
+namespace Ursa.Themes.Semi.Converters;
+
+public class SelectedItemTemplateConverter: IMultiValueConverter
+{
+    public static SelectedItemTemplateConverter Instance { get; } = new SelectedItemTemplateConverter();
+    
+    public object? Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if(values.Count>0 && values[0] is IDataTemplate template1)
+        {
+            return template1;
+        }
+        if(values.Count>1 && values[1] is IDataTemplate template2)
+        {
+            return template2;
+        }
+        return AvaloniaProperty.UnsetValue;
+    }
+}

src/Ursa/Controls/ComboBox/TreeComboBox.cs

@@ -4,19 +4,21 @@ using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Shapes;
 using Avalonia.Controls.Templates;
+using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Metadata;
 using Avalonia.VisualTree;
 using Irihi.Avalonia.Shared.Common;
+using Irihi.Avalonia.Shared.Contracts;
 using Size = Avalonia.Size;
 
 
 namespace Ursa.Controls;
 
 [TemplatePart(PartNames.PART_Popup, typeof(Popup))]
-public class TreeComboBox: ItemsControl
+public class TreeComboBox: ItemsControl, IClearControl
 {
     private Popup? _popup;
     
@@ -89,8 +91,10 @@ public class TreeComboBox: ItemsControl
 
     private object? _selectedItem;
 
-    public static readonly DirectProperty<TreeComboBox, object?> SelectedItemProperty = AvaloniaProperty.RegisterDirect<TreeComboBox, object?>(
+    public static readonly DirectProperty<TreeComboBox, object?> SelectedItemProperty =
-        nameof(SelectedItem), o => o.SelectedItem, (o, v) => o.SelectedItem = v);
+        AvaloniaProperty.RegisterDirect<TreeComboBox, object?>(
+            nameof(SelectedItem), o => o.SelectedItem, (o, v) => o.SelectedItem = v,
+            defaultBindingMode: BindingMode.TwoWay);
 
     public object? SelectedItem
     {
@@ -284,4 +288,9 @@ public class TreeComboBox: ItemsControl
             treeComboBoxItem.IsSelected = selected;
         }
     }
+
+    public void Clear()
+    {
+        SelectedItem = null;
+    }
 }