prevent multiple instances of an application

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prevent multiple instances of an application

How can I prevent multiple instances of a C# windows forms application. VB.NET provides My.Application.StartupNextInstance Event to do this. Is there any C# equivalent as well

Thanks



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prevent multiple instances of an application

  • Jeroen Alblas

    you could do this...

    Process[] theProcesses = System.Diagnostics.Process.GetProcessesByName(Application.ProductName); //maybe add .exe at the end of Application.ProductName

    if (theProcesses.Length > 1)

    {

    MessageBox.Show("There is already another instance of the application running");

    Application.Exit();

    }



  • Mark Pitman

    that works great. how would i set focus to the previous instances.

    thanks



  • Drew Marsh

    I haven't managed to get this to work.  But maybe this will help you go in the right direction.

    First, create an extern to PostMessage:

    [DllImport("User32.Dll")]
    public static extern IntPtr PostMessage(IntPtr hWnd, int msg, int wParam, int lParam);

    Then call that with the window handle of the process you're trying to open with the relevant windows message:

    IntPtr hWnd = Process.GetProcessesByName("iexplore")[0].MainWindowHandle;
    PostMessage(hWnd, 0x18, 0, 0);

    (where 0x18 == WM_SHOWWINDOW)

    Like I say, I haven't got this working yet.  But it seems like a plausible method.  Unfortunately I don't have more time to look into this for you.

     

  • Shihan

    You can use the Process object's MainWindowHandle member and PInvoke the ShowWindow and UpdateWindow Win32 functions. See the Restoring a Previous Instance section at http://www.codeproject.com/csharp/SingleInstanceApplication.asp which contains some information on single instance applications.

  • SoopahMan

    Cool, I knew I was fairly close :)
  • prevent multiple instances of an application
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