You shouldn't be setting this property directly on the editor.  It's actually the owner that is responsible for maintaining this information and providing it to the editor; since you're posting this question in the WinGrid newsgroup, I'm assuming you have this in a grid, which would make the owner the column.  Set the Style property of the column to DropDownList; unless you're doing something like setting a DataFilter, you probably don't need to create the EditorWithCombo either (assuming you are doing so).

-Matt