'Declaration Public Property DropDownButtonDisplayMode As Nullable(Of DropDownButtonDisplayMode)
public Nullable<DropDownButtonDisplayMode> DropDownButtonDisplayMode {get; set;}
DropDownButtonDisplayMode specifies when to display the drop down button. The default value of the property is MouseOver. However note that styles of some of the themes may explicitly set this property to some other value to ensure consistency with the default operating system behavior. For example, the default XamComboEditor style in "Aero" theme used in Windows Vista sets this property to Always.
Note that the drop down button will always be displayed when the editor is in edit mode.
NOTE: If the Infragistics.Windows.Editors.ValueEditor.IsAlwaysInEditMode property is set to True, the drop down button will always be displayed and in effect this property will ignored.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, 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