A ColumnStyle to let you have a combobox column in a .NET DataGrid. The URL is the link where I lifted most of the code from. I fixed a couple of things like showing the DisplayMember not the value member when the item doesn't have focus + I made it so if you select something from the combo box then it makes that row of the DataGrid commit even if no other changes are made.
Object Binding in DataGrid with C#
Grid View Control V - Sizing and Tabbing in the GridView