Having HierarchicalDataTemplates in a TreeView

Question

With regards to a question I posted earlier on (WPF: Correctly storing an object in a TreeViewItem)

Is it possible to have nested HierarchicalDataTemplates in a TreeView?

---

Take the following example:

Code:

public class Artist
{
        private readonly ICollection<Album> _children = new ObservableCollection<Album>();
        public string Name { get; set; }

        public ICollection<Album> Albums
        {
            get { return _children;}
        }
}

public class Album
{
        private readonly ICollection<Track> _children = new ObservableCollection<Track>();
        public string Name { get; set; }

        public ICollection<Track> Tracks
        {
            get { return _children;}
        }
}

Xaml:

<TreeView x:Name="_treeView">
        <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:Artist}" ItemsSource="{Binding Albums}">
                        <TextBlock Text="{Binding Name}"/>
                </HierarchicalDataTemplate>
        </TreeView.Resources>
</TreeView>

As you see from the above, the TreeView is only binding the Artists and their albums. How can I modify it to include also the Tracks of the albums (as a sub-list of the albums ie) ?

Solution

You dont need a nested template here, since TreeView control will take care of nesting it based on the DataType it requires. So just define Two HierarchicalDataTemplates for Album and Artist Type and one ordinary DataTemplate for your Track class.

   <HierarchicalDataTemplate  DataType="{x:Type local:Artist}" ItemsSource="{Binding Albums}" >          
         <TextBlock Text="{Binding Name}"/>                 
    </HierarchicalDataTemplate>
    <HierarchicalDataTemplate  DataType="{x:Type local:Album}" ItemsSource="{Binding Tracks}" >
        <TextBlock Text="{Binding Name}"/>
    </HierarchicalDataTemplate>        
    <DataTemplate DataType="{x:Type local:Track}">
        <TextBlock Text="{Binding Name}"/>
    </DataTemplate>