i believe the control you're looking for is the asp.net DropDownlist. you can either populate it manually or programatically, and even bind database data to it.
here's a helpful resource I've found:http://www.devcity.net/Articles/68/1/aspnet_dropdown.aspx
i hope this is what you were looking for and that this was helpful.
to retreive the selected value on posting, simply use ddl.SelectedValue where ddl is the ID of your control.