How to change HierarchicalDataTemplate? - wpf

Question

How can I change HierarchicalDataTemplate by DataTrigger in my TreeView?
<TreeView Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="2"
ItemsSource="{Binding Nodes}">
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="IsExpanded" Value="True" />
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Nodes}">
<HierarchicalDataTemplate.Triggers>
<DataTrigger Binding="{Binding Type}" Value="group">
<Setter Property="Content">
<Setter.Value>
<TextBlock Text="{Binding Title}" />
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Type}" Value="page">
<Setter Property="Content">
<Setter.Value>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Page.Name}" />
<TextBlock Text="{Binding Page.Format}" />
</StackPanel>
</Setter.Value>
</Setter>
</DataTrigger>
</HierarchicalDataTemplate.Triggers>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
In ItemSource of TreeView i put list of Node objects:
public class Node
{
public string Title { get; set; }
public Page Page { get; set; }
public string Type { get; set; }
public List<Node> Nodes { get; set; } = new List<Node>();
}
And this is the result:
What am I doing wrong?

Answer 1

In WPF, the "correct" way to create complex content is with a template.
I tried the XAML below, and it worked. Where I bind Content="{Binding}" on the inner ContentControl, that just binds the content of the contentcontrol to the DataContext of the parent -- in this case, the Node object.
<TreeView
Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="2"
ItemsSource="{Binding Nodes}"
>
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="IsExpanded" Value="True" />
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Nodes}">
<ContentControl
x:Name="PART_ContentControl"
Content="{Binding}"
/>
<HierarchicalDataTemplate.Triggers>
<DataTrigger Binding="{Binding Type}" Value="Group">
<Setter Property="ContentTemplate" TargetName="PART_ContentControl">
<Setter.Value>
<DataTemplate>
<TextBlock Text="{Binding Title}" />
</DataTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Type}" Value="Page">
<Setter Property="ContentTemplate" TargetName="PART_ContentControl">
<Setter.Value>
<DataTemplate>
<StackPanel Orientation="Vertical">
<TextBlock Text="{Binding Page.Name}" />
<TextBlock Text="{Binding Page.Format}" />
</StackPanel>
</DataTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</HierarchicalDataTemplate.Triggers>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>