Since, this question is tagged with
DevExpress
, the
Popup Control
can be used for this purpose.
A Demo for this control is available here
http://demos.devexpress.com/ASPxperienceDemos/PopupControl/Features.aspx[
^]
On this page select
MouseOver
from the ComboBox as the
PopupAction
which is available at the bottom right side.
Then bring mouse over the
PopupElement
button at the Top left to see the popup control.