Locks the most recent undo unit of the undo stack of the application. This prevents the locked unit from being merged with undo units that are added subsequently.
Assembly: PresentationFramework (in PresentationFramework.dll)
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
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.