[DllImport (" User32. DLL)]
Public static extern int GetDesktopWindow ();

Private IMapDocument mapDocument=null;

Private void ChangeMapScale ()
{
MapDocument. Open (@ "C: \ Temp \ foo MXD", null);

IPageLayout pageLayout=mapDocument. PageLayout;
IActiveView activeView=(IActiveView) pageLayout;
IMap map=activeView. FocusMap;

ActiveView=(IActiveView) mapDocument. PageLayout;
ActiveView. Activate (GetDesktopWindow ());//note that calls the function, to make the Settings take effect MapScale

Map. MapScale=value;
ActiveView. Refresh ();

MapDocument. Save (true, true);
}


Is solved by this method will appear full screen after how remove the full-screen, bosses could help me to solve, thank you!