When I configure it as you've suggested I get the "Input is not in correct Format" validation error.
In my output I get this:
System.Windows.Data Error: ConvertBack cannot convert value '25e2df37-41a6-41b6-aa8f-0d8b2dfa6d73' (type 'System.Guid').
BindingExpression: Path='dms_UnitType' DataItem='MainItem : eb980f34-2318-4ee3-bad8-b1fc51ac6677' (HashCode=6964713);
target element is 'Telerik.Windows.Controls.RadComboBox' (Name='');
target property is 'SelectedValue' (type 'System.Object')..
System.InvalidOperationException: Can't convert type System.Guid to type UnitInventoryService.Web.dms_UnitType.
what you've suggested is basically saying to bind the Guid to the dms_UnitType type.
I get the impression SelectedValueMemberPath is being used for two things, both the display name and the selected Value binding. But in my case they need to be separate values. I need the display to be the name and the binding to be the item from the list (or the ID property).