title: how to binding something to groupstyle's header
body: <p>Using CollectionViewSource can easily grouping the ListBoxItem.
  But each group Header, only have a "Name" data. 
  How to put more data to the Header?</p>
  
  <p>like the picture.</p>
  
  <ol>
  <li>i want to use a custom control in the header, and binding a viewmodel to it.
  but i dont know how to get the viewmodel from the grouping parent.</li>
  <li>and, the <code>&lt;ItemsPresenter/&gt;</code>, groupItem's part.if i want binding something to it, 
  what can i do?</li>
  </ol>
  
  <p>and , my code:</p>
  
  <pre><code>&lt;ListBox ItemsSource="{Binding Source={StaticResource XamlBookMarks}}"
           ItemTemplate="{StaticResource TemplateBookMark}"&gt;
      &lt;ListBox.GroupStyle&gt;
          &lt;GroupStyle ContainerStyle="{StaticResource StyleBookMarkGroup}" /&gt;
      &lt;/ListBox.GroupStyle&gt;
  &lt;/ListBox&gt;
  
   &lt;Style x:Key="StyleWorkSiteGroup" TargetType="{x:Type GroupItem}"&gt;
          &lt;Setter Property="Template"&gt;
              &lt;Setter.Value&gt;
                  &lt;ControlTemplate TargetType="{x:Type GroupItem}"&gt;
                      &lt;StackPanel&gt;
                          &lt;ContentControl Content="{Binding}" ContentTemplate="{StaticResource TemplateHeader}" /&gt;
                          &lt;!--here, i want binding something to ItemsPresenter--&gt;
                          &lt;ItemsPresenter/&gt;
                      &lt;/StackPanel&gt;
                  &lt;/ControlTemplate&gt;
              &lt;/Setter.Value&gt;
          &lt;/Setter&gt;
      &lt;/Style&gt;
  
       &lt;DataTemplate x:Key="TemplateHeader" DataType="{x:Type GroupItem}"&gt;
          &lt;DockPanel&gt;
              &lt;DockPanel.Resources&gt;
                  &lt;converters:HeaderGetter x:Key="HeaderConverter" /&gt;
              &lt;/DockPanel.Resources&gt;
              &lt;ContentControl DockPanel.Dock="Top" Content="{Binding Name, Converter={StaticResource HeaderConverter}, ConverterParameter={StaticResource XamlHeaders}}"&gt;
                  &lt;ContentControl.Resources&gt;
                      &lt;DataTemplate DataType="{x:Type local:GroupOneHeaderViewModel}"&gt;
                          &lt;views:GroupOneHeaderView /&gt;
                      &lt;/DataTemplate&gt;
                      &lt;DataTemplate DataType="{x:Type local:GroupTwoHeaderViewModel}"&gt;
                          &lt;views:GroupTwoHeaderView /&gt;
                      &lt;/DataTemplate&gt;
                  &lt;/ContentControl.Resources&gt;
              &lt;/ContentControl&gt;
          &lt;/DockPanel&gt;
      &lt;/DataTemplate&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/zAFf6.png" alt="enter image description here"></p>