IsWorking will be set to true by the base class when OnWorkStarted is called. It will be set back to false when OnWorkCompleted is called.
This value is useful when deriving your own interactive mode classes. Refer to ImageViewerInteractiveMode for an example.
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