DataGridComboBoxColumn help needed (WPF DataGrid)

Question

I've tried reading a lot of tutorials, but none have helped.

Here is what I want to do.

First.... start simple I want to turn a regular DataGridTextColumn into a DataGridComboBoxColumn. E.g just display the cell text on the dropdown, and doesn't matter if the dropdownlist is empty. I havn't even managed to do this

e.g From

`<dg:DataGridTextColumn Binding="{Binding Path=ApplicationName}" Header="ApplicationName" />`

(this works, and displays data)

To

`<dg:DataGridComboBoxColumn ????????? Header="ApplicationName" />`

(whatever I put never works)

If someone can please help me with that, then I'll go away and have a play, and come back with the next thing I want to do if I can't figure it out

Complete code if needed. Posted at Pastbin cause got no idea how to do codeblocks here http://pastebin.com/CU6VLQhg