title: WPF Bindings TreeView Issue with view
body: <p>I'm simply trying to bind my tree view in xaml but for some reason the list does not seem to be showing, I have attached the code. Any help would be great. </p>
  
  <p>Many thanks </p>
  
  <pre><code>class Item
  {
      public string Header { get; set; }
      public List&lt;string&gt; TreeItems { get; set; }
      public List&lt;Item&gt; SubItems { get; set; }
  }
  </code></pre>
  
  <p>this is the view model</p>
  
  <pre><code>    public StoreLibraryViewModel()
      {
          this.DisplayName = "hierarchy Library";
          TreeItems = new ObservableCollection&lt;Item&gt;();
  
          string[] data = new string[]{
              "Warwick","Birmingham",
          };
          Item item = new Item()
          {
              Header = "Region",
              TreeItems = new List&lt;string&gt;(data)
          };
  
          TreeItems.Add(new Item()
          {
              Header = "Region 1",
              SubItems = new List&lt;Item&gt;(new Item[] { item }),
              TreeItems = new List&lt;string&gt;(data)
          });
          TreeItems.Add(new Item()
          {
              Header = "Region 2",
              SubItems = new List&lt;Item&gt;(new Item[] { item }),
              TreeItems = new List&lt;string&gt;(data)
          });
  
          TreeItems.Add(new Item()
          {
              Header = "Region 3",
              SubItems = new List&lt;Item&gt;(new Item[] { item }),
              TreeItems = new List&lt;string&gt;(data)
          });
      }
      ObservableCollection&lt;Item&gt; TreeItems { get; set; }
  </code></pre>
  
  <p>this is the XAML</p>
  
  <pre><code>TreeView ItemsSource="{Binding TreeItems}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"&gt;
          &lt;TreeView.ItemTemplate&gt;
              &lt;HierarchicalDataTemplate ItemsSource="{Binding SubItems}"&gt;
                  &lt;Expander Header="{Binding Header}"&gt;
                      &lt;ItemsControl Margin="25,0,0,0" ItemsSource="{Binding TreeItems}" /&gt;
                  &lt;/Expander&gt;
              &lt;/HierarchicalDataTemplate&gt;
          &lt;/TreeView.ItemTemplate&gt;
      &lt;/TreeView&gt;
  </code></pre>
  
  <p>All I seem to be displaying is a empty tree view, any assistance would be greatly appreciated.</p>
  
  <p>Many Thanks  </p>