title: Group Style Header never appears
body: <p>My GroupStyle Header never appears in the combobox....</p>
  
  <p>The Grouping is working fine....It's sole a binding issue but am not able to figure out.</p>
  
  <pre><code>&lt;ComboBox Height="23" Margin="33,45,125,0" Name="comboBox1" VerticalAlignment="Top"  ItemsSource="{Binding}" &gt;
      &lt;ComboBox.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;Border Background="Red"&gt;
                  &lt;TextBlock Text="{Binding Path=value}" /&gt;
              &lt;/Border&gt;
          &lt;/DataTemplate&gt;
      &lt;/ComboBox.ItemTemplate&gt;
      &lt;ComboBox.GroupStyle&gt;
          &lt;GroupStyle&gt;
              &lt;GroupStyle.HeaderTemplate&gt;
                  &lt;DataTemplate&gt;
                      &lt;StackPanel&gt;
                          &lt;TextBlock FontSize="12" FontWeight="Bold" Foreground="DarkGray"&gt;
                              &lt;Button Content="{Binding Path=Location}"/&gt;
                              &lt;TextBlock  Text="{Binding Path=Location}" /&gt;
                              &lt;Button&gt;bbbb&lt;/Button&gt;
  
                          &lt;/TextBlock&gt;
                          &lt;ItemsPresenter/&gt;
                      &lt;/StackPanel&gt;
                  &lt;/DataTemplate&gt;
              &lt;/GroupStyle.HeaderTemplate&gt;
          &lt;/GroupStyle&gt;
      &lt;/ComboBox.GroupStyle&gt;
  &lt;/ComboBox&gt;
  </code></pre>
  
  <p>and code behind</p>
  
  <pre><code>public class Store
  {
      public string Location { get; set; }
      public string value { get; set; }
  }
  
  public partial class Window1 : Window
  {
      public Window1()
      {
          InitializeComponent();
  
          var myData = new ObservableCollection&lt;Store&gt;
          {
              new Store { Location = "Group1", value = "Item 1" },
              new Store { Location = "Bombay", value = "Item 2" },
              new Store { Location = "Group2", value = "Item 11" }
          }
  
          ICollectionView view = CollectionViewSource.GetDefaultView(myData);
          view.GroupDescriptions.Add(new PropertyGroupDescription("Location"));
  
          DataContext = myData;
      }
  }
  </code></pre>