It seems that we have a misunderstanding of what exactly you expect from the combobox, because from what we understood about your requirement, MS ComboBox is not working. However, considering your latest statement, it seems that your requirement is different. Please describe the exact scenario that you want to achieve. Provide us with a details step-by-step guide of the steps that you performed (in the attached project) and the result that you achieved and that is expected.
Thank you for your cooperation. I am looking forward to your response.
the Telerik team
Q3’10 SP1 of RadControls for WinForms is available for download
; also available is the Q1'11 Roadmap
for Telerik Windows Forms controls.