I have implemented using the examples in the forum a combobox with a treeview in the itemtemplate. The problem i am having is that the Itemtemplate consumes the entire dropdown area and the "all categories" item i have is not available in the dropdown list. I am using the dropdowns as filters so i need the user to be able to clear the selection. See example below. The "all categories" item is displayed in the combo text box on initial load. When the combo is expanded "all categories" is not a selecteble item. Once the user selects a category there is no way for them to reset the filter to "all categories". Is this by design?