WPF TreeViewItem Control Template Partially applied? - wpf

Question

I know a ControlTemplate is suppose to replace the default one entirely and this seems to work when not using a HierarchicalDataTemplate. However using a HierarchicalDataTemplate my control template seems to be partially used - the TreeViewItem is the control I specified containing an image etc. BUT still appears as a node with the default expander to show its children - not specified in my Template (I want my children to always be shown, but thats beside the point). It looks like this:
<TreeView>
<TreeView.Resources>
<Style x:Key="MyNodeStyle" TargetType="TreeViewItem">
<Setter Property="SnapsToDevicePixels" Value="true" />
<Setter Property="OverridesDefaultStyle" Value="true"/>
<Setter Property="IsExpanded" Value="true"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeViewItem">
<StackPanel Orientation="Vertical" HorizontalAlignment="Center">
<Border CornerRadius="8" BorderThickness="1" Padding="2" Margin="4, 6" BorderBrush="{StaticResource itemBorderBrush}" Background="{StaticResource itemBackgroundBrush}" x:Name="border">
<DockPanel LastChildFill="False">
<StackPanel Orientation="Vertical" DockPanel.Dock="Top" Height="80">
<TextBlock Text="{Binding Path=DisplayValue}" HorizontalAlignment="Center" FontWeight="Bold"/>
<Image Source="MyNode.png" Stretch="None"/>
<TextBlock Text="{Binding Path=Notes}" TextWrapping="Wrap" Width="150"/>
</StackPanel>
</DockPanel>
</Border>
<ItemsPresenter />
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" IsItemsHost="True" HorizontalAlignment="Center" />
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Style>
<HierarchicalDataTemplate DataType="{x:Type src:MyNode}" ItemsSource="{Binding Path=Children}" >
<TreeViewItem Style="{StaticResource MyNodeStyle}"/>
</HierarchicalDataTemplate>
</TreeView.Resources>
<!-- Arrange the root items horizontally. -->
<TreeView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel IsItemsHost="True" Orientation="Horizontal" HorizontalAlignment="Center" />
</ItemsPanelTemplate>
</TreeView.ItemsPanel>
</TreeView>
For some reason only when using a HierarchicalDataTemplate the ItemsPanel and Setter does not seem to be applied and the children are presented in the default expander. How did that expander get there when I am using my own ControlTemplate!?##$

Answer 1

I don't think you should put the TreeViewItem inside your HierarchicalDataTemplate.
Try this:
<HierarchicalDataTemplate DataType="{x:Type src:MyNode}" ItemsSource="{Binding Path=Children}" >
<StackPanel Orientation="Vertical" DockPanel.Dock="Top" Height="80">
<TextBlock Text="{Binding Path=DisplayValue}" HorizontalAlignment="Center" FontWeight="Bold"/>
<Image Source="MyNode.png" Stretch="None"/>
<TextBlock Text="{Binding Path=Notes}" TextWrapping="Wrap" Width="150"/>
</StackPanel>
</HierarchicalDataTemplate>
Now, your template becomes:
<ControlTemplate TargetType="TreeViewItem">
<StackPanel Orientation="Vertical" HorizontalAlignment="Center">
<Border CornerRadius="8" BorderThickness="1" Padding="2" Margin="4, 6" x:Name="border">
<DockPanel LastChildFill="False">
<ContentPresenter ContentSource="Header" />
</DockPanel>
</Border>
<ItemsPresenter />
</StackPanel>
</ControlTemplate>
Is that how you intended it to look?
Edit: the original expanders are probably there because you only use your style for child items - make your style the ItemContainerStyle for the treeview:
<Window.Resources>
<Style x:Key="MyNodeStyle" TargetType="TreeViewItem">
....
<TreeView ItemContainerStyle="{StaticResource MyNodeStyle}">