How do I use the DataType property on a WPF DataTemplate?

Question

So obviously I am doing something wrong, but I just cannot seem to get the HierarchicalDataTemplate (or even just DataTemplate) to work when using the DataType property. I have created the shortest possible WPF application to demonstrate the problem.

XAML:

<Window x:Class="WpfApplication1.Window1"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:System="clr-namespace:System;assembly=mscorlib"     xmlns:local="clr-namespace:WpfApplication1"     Title="Window1" Height="300" Width="300" Loaded="Window_Loaded">     <Window.Resources>         <HierarchicalDataTemplate DataType="x:Type local:Foo">             <TextBlock Text="I am a Foo" />         </HierarchicalDataTemplate>         <HierarchicalDataTemplate DataType="x:Type System:String">             <TextBlock Text="I am a String" />         </HierarchicalDataTemplate>     </Window.Resources>     <Grid>         <TreeView Name="treeView1" ItemsSource="{Binding}" />     </Grid> </Window> 

CODE:

namespace WpfApplication1 {     public class Foo     {         public string Name { get; set; }     }      public partial class Window1 : Window     {         public Window1()         {             InitializeComponent();         }          private void Window_Loaded(object sender, RoutedEventArgs e)         {             var list = new List<object> { "a", 1, "b", 2, new Foo() { Name="Brian"}};             treeView1.DataContext = list;         }     } } 

Obviously I am expecting it display the following in the treeview.

I am a string 1 I am a string 2 I am a foo 

But my application actually displays the following.

a 1 b 2 WpfApplication1.Foo 

The strange thing is that almost every example I see on the web does this very thing (with slight variations) and no one else seems to be having a problem with it. Yet I have tried countless different ways of rearranging the XAML and nothing seems to help. I am hoping another pair eyes can help.

Answer 1

Your code is fine, but your DataType attribute values need to be wrapped in curly braces:

<HierarchicalDataTemplate DataType="{x:Type local:Foo}">     <TextBlock Text="I am a Foo" /> </HierarchicalDataTemplate> <HierarchicalDataTemplate DataType="{x:Type System:String}">     <TextBlock Text="I am a String" /> </HierarchicalDataTemplate>