Please find a attached a project which shows the proper Templates you need and how to load the ItemSource in code behind:
this.toolbox.ItemsSource = new HierarchicalGalleryItemsCollection();
Actually both the XAML and code behind are similar to the ones in our DiagramToolBox Demo.
Greetings,
Petar Mladenov
the Telerik team
Time to cast your vote for Telerik! Tell DevPro Connections and Windows IT Pro why Telerik is your choice. Telerik is nominated in a total of 25 categories.