If this property is DialogType.InternalWindowWithTitlebar, the dialog will be a "Windows-style" dialog, complete with titlebar. This type of dialog is draggable with the mouse. If this property is InternalWindow, the dialog will be a titlebar-less panel which is non-draggable. This property only needs to be set for custom dialog implementations, as in predefined dialogs this property will already be configured to the appropriate value for the dialog.
Target Platforms: Windows 10, Windows 8.1, Windows 8, 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