implement TreeDataGrid

src/MainDemo.Wpf/Trees.xaml

@@ -214,9 +214,8 @@
                                      ItemsSource="{Binding TreeItems}"
                                      SelectedItem="{Binding SelectedTreeItem}">
             <materialDesign:TreeListView.Resources>
-              <HierarchicalDataTemplate DataType="{x:Type domain:TestItem}"
-                          ItemsSource="{Binding Items, Mode=OneTime}">
-                <TextBlock Margin="3,2" Text="{Binding Name, Mode=OneTime}" />
+              <HierarchicalDataTemplate DataType="{x:Type domain:TestItem}" ItemsSource="{Binding Items, Mode=OneTime}">
+                  <TextBlock VerticalAlignment="Center" Text="{Binding Name, Mode=OneTime}" />
               </HierarchicalDataTemplate>
 
               <HierarchicalDataTemplate DataType="{x:Type domain:MovieCategory}"
@@ -231,19 +230,41 @@
               </DataTemplate>
             </materialDesign:TreeListView.Resources>
 
-            <!--
-            Because Data Virtualization is enabled on this tree view by default, if you don't bind the IsExpanded property to something in the bound view model,
-            you can loose the expanded state of items when the TreeListViewItem is recycled.
-
-            For more information:
-            https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/issues/3640#issuecomment-2274086113
-            https://learn.microsoft.com/dotnet/desktop/wpf/advanced/optimizing-performance-controls?view=netframeworkdesktop-4.8&WT.mc_id=DT-MVP-5003472
-            -->
+             <!--
+             Because Data Virtualization is enabled on this tree view by default, if you don't bind the IsExpanded property to something in the bound view model,
+             you can loose the expanded state of items when the TreeListViewItem is recycled.
+   
+             For more information:
+             https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/issues/3640#issuecomment-2274086113
+             https://learn.microsoft.com/dotnet/desktop/wpf/advanced/optimizing-performance-controls?view=netframeworkdesktop-4.8&WT.mc_id=DT-MVP-5003472
+             -->
             <materialDesign:TreeListView.ItemContainerStyle>
               <Style TargetType="materialDesign:TreeListViewItem" BasedOn="{StaticResource {x:Type materialDesign:TreeListViewItem}}">
                 <Setter Property="IsExpanded" Value="{Binding IsExpanded}" />
               </Style>
             </materialDesign:TreeListView.ItemContainerStyle>
+
+            <!--<materialDesign:TreeListView.View>
+              <GridView>
+                <GridView.Columns>
+                  <GridViewColumn Width="250" Header="Name">
+                    <GridViewColumn.CellTemplate>
+                      <DataTemplate>
+                        <TextBlock VerticalAlignment="Center" Text="{Binding Name, Mode=OneTime}" />
+                      </DataTemplate>
+                    </GridViewColumn.CellTemplate>
+                  </GridViewColumn>
+
+                  <GridViewColumn Width="100" Header="Count">
+                    <GridViewColumn.CellTemplate>
+                      <DataTemplate>
+                        <TextBlock VerticalAlignment="Center" Text="{Binding Items.Count, Mode=OneWay}" />
+                      </DataTemplate>
+                    </GridViewColumn.CellTemplate>
+                  </GridViewColumn>
+                </GridView.Columns>
+              </GridView>
+            </materialDesign:TreeListView.View>-->
           </materialDesign:TreeListView>
           <StackPanel Orientation="Horizontal" VerticalAlignment="Bottom" HorizontalAlignment="Right">
             <Button Command="{Binding AddListTreeItemCommand}"

src/MaterialDesignThemes.Wpf/Converters/Internal/ViewIsGridViewConverter.cs

@@ -0,0 +1,18 @@
+using System.Globalization;
+using System.Windows.Data;
+
+namespace MaterialDesignThemes.Wpf.Converters.Internal;
+
+internal class ViewIsGridViewConverter : IValueConverter
+{
+    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+    {
+        // Returns true if value is a GridView, otherwise false
+        return value is GridView;
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+    {
+        throw new NotSupportedException();
+    }
+}

src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TreeListView.xaml

@@ -1,11 +1,14 @@
 <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:converters="clr-namespace:MaterialDesignThemes.Wpf.Converters"
-                    xmlns:wpf="clr-namespace:MaterialDesignThemes.Wpf"
-                    xmlns:internal="clr-namespace:MaterialDesignThemes.Wpf.Internal">
+                    xmlns:internalConverters="clr-namespace:MaterialDesignThemes.Wpf.Converters.Internal"
+                    xmlns:internal="clr-namespace:MaterialDesignThemes.Wpf.Internal"
+                    xmlns:wpf="clr-namespace:MaterialDesignThemes.Wpf">
+  <internalConverters:ViewIsGridViewConverter x:Key="ViewIsGridViewConverter" />
 
   <Style x:Key="MaterialDesignTreeListViewToggleButtonStyle" TargetType="{x:Type ToggleButton}">
     <Setter Property="Background" Value="Transparent" />
+    <Setter Property="Foreground" Value="{Binding Foreground, RelativeSource={RelativeSource AncestorType=wpf:TreeListViewItem}}" />
     <Setter Property="Focusable" Value="False" />
     <Setter Property="Height" Value="16" />
     <Setter Property="Template">
@@ -78,6 +81,11 @@
               </Canvas>
             </Viewbox>
           </Border>
+          <ControlTemplate.Triggers>
+            <DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type wpf:TreeListViewItem}}, Path=HasItems}" Value="false">
+              <Setter Property="Visibility" Value="Hidden" />
+            </DataTrigger>
+          </ControlTemplate.Triggers>
         </ControlTemplate>
       </Setter.Value>
     </Setter>
@@ -104,11 +112,14 @@
     <Setter Property="Template">
       <Setter.Value>
         <ControlTemplate TargetType="{x:Type wpf:TreeListViewItem}">
-          <Grid>
+          <Grid x:Name="ItemGrid">
             <Grid.Margin>
               <MultiBinding Converter="{x:Static converters:TreeListViewIndentConverter.Instance}">
-                <Binding Path="LevelIndentSize" RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type wpf:TreeListView}}" FallbackValue="16" />
-                <Binding Path="Level" RelativeSource="{RelativeSource TemplatedParent}" />
+                <Binding Path="LevelIndentSize"
+                         RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type wpf:TreeListView}}"
+                         FallbackValue="16" />
+                <Binding Path="Level"
+                         RelativeSource="{RelativeSource TemplatedParent}" />
               </MultiBinding>
             </Grid.Margin>
             <Grid.ColumnDefinitions>
@@ -173,7 +184,6 @@
                           Foreground="{TemplateBinding Foreground}"
                           IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}"
                           Style="{StaticResource MaterialDesignTreeListViewToggleButtonStyle}" />
-
             <Border x:Name="MouseOverBorder"
                     Grid.Column="1"
                     Grid.ColumnSpan="2"
@@ -198,8 +208,19 @@
                           VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                           Feedback="{TemplateBinding Foreground, Converter={x:Static converters:BrushRoundConverter.Instance}}"
                           Focusable="False"
+                          Foreground="{TemplateBinding Foreground}"
                           SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}">
-                <internal:TreeListViewContentPresenter x:Name="PART_ContentPresenter" ContentSource="Content" />
+                <Grid Margin="0,0,0,0">
+                  <internal:TreeListViewContentPresenter x:Name="PART_ContentPresenter"
+                                                         ContentSource="Content"
+                                                         Visibility="Visible" />
+
+                  <GridViewRowPresenter x:Name="PART_GridViewRowPresenterr"
+                                        Margin="{TemplateBinding Padding}"
+                                        VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
+                                        SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
+                                        Visibility="Collapsed" />
+                </Grid>
               </wpf:Ripple>
             </Grid>
 
@@ -219,9 +240,6 @@
             <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=(wpf:TreeViewAssist.AdditionalTemplateSelector), Converter={x:Static converters:NullableToVisibilityConverter.CollapsedInstance}, Mode=OneWay}" Value="Visible">
               <Setter TargetName="AdditionalContentControl" Property="Visibility" Value="Visible" />
             </DataTrigger>
-            <Trigger Property="HasItems" Value="false">
-              <Setter TargetName="Expander" Property="Visibility" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(wpf:TreeViewAssist.HasNoItemsExpanderVisibility)}" />
-            </Trigger>
             <Trigger Property="IsEnabled" Value="false">
               <Setter Property="Opacity" Value=".56" />
             </Trigger>
@@ -230,6 +248,12 @@
               <Setter TargetName="Ripple" Property="Feedback" Value="Transparent" />
               <Setter TargetName="SelectedBorder" Property="Visibility" Value="Collapsed" />
             </DataTrigger>
+            <DataTrigger Binding="{Binding View, RelativeSource={RelativeSource AncestorType=wpf:TreeListView}, Converter={StaticResource ViewIsGridViewConverter}}" Value="True">
+              <Setter TargetName="PART_ContentPresenter" Property="Visibility" Value="Hidden" />
+              <Setter TargetName="PART_GridViewRowPresenterr" Property="Visibility" Value="Visible" />
+              <Setter TargetName="Expander" Property="Visibility" Value="Collapsed" />
+              <Setter TargetName="ItemGrid" Property="Margin" Value="0" />
+            </DataTrigger>
           </ControlTemplate.Triggers>
         </ControlTemplate>
       </Setter.Value>
@@ -245,6 +269,7 @@
     <Setter Property="BorderBrush" Value="{x:Null}" />
     <Setter Property="BorderThickness" Value="0" />
     <Setter Property="Foreground" Value="{DynamicResource MaterialDesign.Brush.Foreground}" />
+    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
     <Setter Property="Padding" Value="1" />
     <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
     <Setter Property="ScrollViewer.PanningMode" Value="Both" />
@@ -257,6 +282,7 @@
                   BorderThickness="{TemplateBinding BorderThickness}"
                   SnapsToDevicePixels="true">
             <ScrollViewer x:Name="PART_ScrollViewer"
+                          Style="{DynamicResource {x:Static GridView.GridViewScrollViewerStyleKey}}"
                           wpf:ScrollViewerAssist.IgnorePadding="{Binding Path=(wpf:ScrollViewerAssist.IgnorePadding), RelativeSource={RelativeSource TemplatedParent}}"
                           wpf:ScrollViewerAssist.PaddingMode="{Binding Path=(wpf:ScrollViewerAssist.PaddingMode), RelativeSource={RelativeSource TemplatedParent}}"
                           Padding="{TemplateBinding Padding}"

src/MaterialDesignThemes.Wpf/TreeListView.cs

@@ -1,12 +1,15 @@
+using System.Collections;
 using System.Collections.Specialized;
 using System.Windows.Automation.Peers;
+using System.Windows.Data;
+
 using MaterialDesignThemes.Wpf.Automation.Peers;
+using MaterialDesignThemes.Wpf.Converters;
 using MaterialDesignThemes.Wpf.Internal;
 
 namespace MaterialDesignThemes.Wpf;
 
 //TODO: Implement bindable property for getting selected items
-//TODO: Implement GridView support for having columns
 public class TreeListView : ListView
 {
     public double LevelIndentSize
@@ -259,4 +262,68 @@ internal void MoveSelectionToParent(TreeListViewItem item)
             }
         }
     }
+
+    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
+    {
+        base.OnPropertyChanged(e);
+
+        if (e.Property == ViewProperty)
+        {
+            if (View is GridView gridView)
+            {
+                AddToggleButtonToFirstColumn(gridView);
+            }
+        }
+    }
+
+    private void AddToggleButtonToFirstColumn(GridView gridView)
+    {
+        if (gridView.Columns.Count > 0)
+        {
+            var firstColumn = gridView.Columns[0];
+            firstColumn.CellTemplate = CreateToggleButtonTemplate(firstColumn.CellTemplate);
+        }
+    }
+
+    private DataTemplate CreateToggleButtonTemplate(DataTemplate originalTemplate)
+    {
+        var template = new DataTemplate();
+
+        var stackPanelFactory = new FrameworkElementFactory(typeof(StackPanel));
+        stackPanelFactory.SetValue(StackPanel.OrientationProperty, Orientation.Horizontal);
+
+        var marginMultiBinding = new MultiBinding
+        {
+            Converter = TreeListViewIndentConverter.Instance,
+        };
+        marginMultiBinding.Bindings.Add(new Binding(LevelIndentSizeProperty.Name)
+        {
+            RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor, typeof(TreeListView), 1)
+        });
+        marginMultiBinding.Bindings.Add(new Binding(TreeListViewItem.LevelProperty.Name)
+        {
+            RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor, typeof(TreeListViewItem), 1)
+        });
+        stackPanelFactory.SetBinding(StackPanel.MarginProperty, marginMultiBinding);
+
+        var toggleButtonFactory = new FrameworkElementFactory(typeof(ToggleButton));
+        toggleButtonFactory.SetValue(ToggleButton.StyleProperty, Application.Current.Resources["MaterialDesignTreeListViewToggleButtonStyle"]);
+
+        toggleButtonFactory.SetBinding(ToggleButton.IsCheckedProperty, new Binding(TreeListViewItem.IsExpandedProperty.Name)
+        {
+            RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor, typeof(TreeListViewItem), 1)
+        });
+
+        stackPanelFactory.AppendChild(toggleButtonFactory);
+
+        if (originalTemplate != null)
+        {
+            var originalContentFactory = new FrameworkElementFactory(typeof(ContentPresenter));
+            originalContentFactory.SetValue(ContentPresenter.ContentTemplateProperty, originalTemplate);
+            stackPanelFactory.AppendChild(originalContentFactory);
+        }
+
+        template.VisualTree = stackPanelFactory;
+        return template;
+    }
 }