KB109059 - How To Prevent Multiple Instances of an Application

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NOTE: This works in Windows for Workgroups 3.00, Windows 95, and Windows NT.

Copy this code into a program file in FoxPro for windows. The first time you call the program, you will notice the main FoxPro window title change. The second time you run it, you will get the message that you cannot start another instance of the window.

NOTE: Set the window name after you check for its existence.

   SET LIBRARY TO SYS(2004)+"foxtools.fll" ADDITIVE
   * FindWindow() takes two parameters and returns the handle of the
   * window, HWND, if it was found.
   GetWind = RegFn("FindWindow", "CC", "I")
   *Set the first parameter of the call to getwind to 0, null.
   wclass=0
   winname="My Application"
   apphand=CallFn(GetWind,wclass ,winname)
   *If the call was successful, stop processing.
   IF apphand<>0
      WAIT WINDOW ;
        "You cannot start another instance of the window 'My Application'!"
      QUIT
   ENDIF
   MODIFY WINDOW screen TITLE "My Application"
   WAIT WINDOW ;
     "The first instance of the window 'My Application' is running."

How To Prevent Multiple Instances of an Application

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