I'm converting to the WPF DataGrid from the .Net WinForms version. The transition is killing me!

One thing I've noticed right away is the GroupByHeader grouped value displays the underlying bound data, rather than the content from the CellContentTemplate. I'm running across this with the ComboBox using the DataTableDictionary examples. 

The .net version of the DataGrid had both a ComboBoxEditor and ComboBoxView control that accurately displayed the underlying DisplayMemberPath. It sure would be nice to have an equivalent ComboBoxViewer control (perhaps derived from a combobox control template without the button and pop-up parts) for WPF.

In lieu of that,  how can I change the display of the GroupBy so that it uses the bound data but with the correct display template?

 BTW, the DataTableDictionary sample is not the best solution to the ContentTemplate display problem with comboboxes. Most times this data comes from relational tables, and these are difficult to initialize in XAML and/or class objects - especially if you don't have a DataConnection yet.