true if the dropdown portion is displayed; false otherwise. By default false.
Remarks
If the AllowDropDown property is set to false, an exception will be thrown when trying to open the DropDownControl.
Requirements
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2