how to bind data to group header of listview in wpf?

Hi All,

I have a ListView, and I want to add grouping to it.  I added a CollectionViewSource, and set my grouping and sorting parameters.  I then written a GroupStyle to my XAML.  It works as expected, except for a text fields I try to bind to in the header (I have a name to show in the header).  The text fields show up blank, even though the data is there (I am sure the data is here because one column is to show this data).  Here is the XAML snippet: 

<GroupStyle ><GroupStyle.HeaderTemplate><DataTemplate><Border><StackPanel Height="30"  Grid.Row="0" Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Left"><TextBlock Text="{Binding DisplayName}" VerticalAlignment="Center" HorizontalAlignment="Left" /></StackPanel></Border></DataTemplate></GroupStyle.HeaderTemplate></GroupStyle>

I have seen a similar problem(http://social.msdn.microsoft.com/Forums/vstudio/en-US/6c9f8e0b-8b5c-4c8c-a432-817cb8e05ae2/problem-with-data-binding-and-group-header-on-listview) but I try its solution and it does not work for me. 

Any Ideas? Thanks.