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C# Force Form Focus

Asked 2008-09-05T15:25:11.030
25

So, I did search google and SO prior to asking this question. Basically I have a DLL that has a form compiled into it. The form will be used to display information to the screen. Eventually it will be asynchronous and expose a lot of customization in the dll. For now I just want it to display properly. The problem that I am having is that I use the dll by loading it in a Powershell session. So when I try to display the form and get it to come to the top and have focus, It has no problem with displaying over all the other apps, but I can't for the life of me get it to display over the Powershell window. Here is the code that I am currently using to try and get it to display. I am sure that the majority of it won't be required once I figure it out, this just represents all the things that I found via google.

CLass Blah
{
        [DllImport("user32.dll", EntryPoint = "SystemParametersInfo")]
        public static extern bool SystemParametersInfo(uint uiAction, uint uiParam, uint pvParam, uint fWinIni);

        [DllImport("user32.dll", EntryPoint = "SetForegroundWindow")]
        public static extern bool SetForegroundWindow(IntPtr hWnd);

        [DllImport("User32.dll", EntryPoint = "ShowWindowAsync")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        private const int WS_SHOWNORMAL = 1;

    public void ShowMessage(string msg)
    {
            MessageForm msgFrm = new MessageForm();
            msgFrm.lblMessage.Text = "FOO";
            msgFrm.ShowDialog();
            msgFrm.BringToFront();
            msgFrm.TopMost = true;
            msgFrm.Activate();

            SystemParametersInfo((uint)0x2001, 0, 0, 0x0002 | 0x0001);
            ShowWindowAsync(msgFrm.Handle, WS_SHOWNORMAL);
            SetForegroundWindow(msgFrm.Handle);
            SystemParametersInfo((uint)0x2001, 200000, 200000, 0x0002 | 0x0001);
    }
}

As I say I'm sure that most of that is either not needed or even flat out

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4 Answers

16

Here is some code that I've used on one form or another for a few years. There are a few gotchas to making a window in another app pop up. Once you have the window handle do this:

      if (IsIconic(hWnd))
        ShowWindowAsync(hWnd, SW_RESTORE);

      ShowWindowAsync(hWnd, SW_SHOW);

      SetForegroundWindow(hWnd);

      // Code from Karl E. Peterson, www.mvps.org/vb/sample.htm
      // Converted to Delphi by Ray Lischner
      // Published in The Delphi Magazine 55, page 16
      // Converted to C# by Kevin Gale
      IntPtr foregroundWindow = GetForegroundWindow();
      IntPtr Dummy = IntPtr.Zero;

      uint foregroundThreadId = GetWindowThreadProcessId(foregroundWindow, Dummy);
      uint thisThreadId       = GetWindowThreadProcessId(hWnd, Dummy);

      if (AttachThreadInput(thisThreadId, foregroundThreadId, true))
      {
        BringWindowToTop(hWnd); // IE 5.5 related hack
        SetForegroundWindow(hWnd);
        AttachThreadInput(thisThreadId, foregroundThreadId, false);
      }

      if (GetForegroundWindow() != hWnd)
      {
        // Code by Daniel P. Stasinski
        // Converted to C# by Kevin Gale
        IntPtr Timeout = IntPtr.Zero;
        SystemParametersInfo(SPI_GETFOREGROUNDLOCKTIMEOUT, 0, Timeout, 0);
        SystemParametersInfo(SPI_SETFOREGROUNDLOCKTIMEOUT, 0, Dummy, SPIF_SENDCHANGE);
        BringWindowToTop(hWnd); // IE 5.5 related hack
        SetForegroundWindow(hWnd);
        SystemParametersInfo(SPI_SETFOREGROUNDLOCKTIMEOUT, 0, Timeout, SPIF_SENDCHANGE);
      }

I won't post the whole unit since since it does other things that aren't relevant but here are the constants and imports for the above code. 

//Win32 API calls necesary to raise an unowned processs main window

[DllImport("user32.dll")]

private static extern bool SetForegroundWindow(IntPtr hWnd);
[DllImport("user32.dll")]
private static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
[DllImport("user32.dl
answered 2008-09-18T17:23:23.273
1

Huge thanks people.
I think I've made it a bit shorter, here's what I put on a seperate thread and seems to be working ok.

private static void StatusChecking()
{
    IntPtr iActiveForm = IntPtr.Zero, iCurrentACtiveApp = IntPtr.Zero;
    Int32 iMyProcID = Process.GetCurrentProcess().Id, iCurrentProcID = 0;
    IntPtr iTmp = (IntPtr)1;

    while (bIsRunning)
    {
        try
        {
            Thread.Sleep(45);
            if (Form.ActiveForm != null)
            {
                iActiveForm = Form.ActiveForm.Handle;
            }
            iTmp = GetForegroundWindow();
            if (iTmp == IntPtr.Zero) continue;
            GetWindowThreadProcessId(iTmp, ref iCurrentProcID);
            if (iCurrentProcID == 0)
            {
                iCurrentProcID = 1;
                continue;
            }
            if (iCurrentProcID != iMyProcID)
            {
                SystemParametersInfo(SPI_GETFOREGROUNDLOCKTIMEOUT, 0, IntPtr.Zero, 0);
                SystemParametersInfo(SPI_SETFOREGROUNDLOCKTIMEOUT, 0, IntPtr.Zero, SPIF_SENDCHANGE);
                BringWindowToTop(iActiveForm);
                SetForegroundWindow(iActiveForm);
            }
            else iActiveForm = iTmp;
        }
        catch (Exception ex)
        {
            Definitions.UnhandledExceptionHandler(ex, 103106);
        }
    }
}

I don`t bother repasting the definitions...

answered 2009-04-04T17:12:59.600
0

You shouldn't need to import any win32 functions for this. If .Focus() isn't enough the form should also have a .BringToFront() method you can use. If that fails, you can set it's .TopMost property to true. You don't want to leave it true forever, so then call Application.DoEvents so the form can process that message and set it back to false.

answered 2008-09-05T16:16:39.220
0

Don't you just want the dialog to be a child of the calling form?

To do that you'll need the pass in the calling window and use the ShowDialog( IWin32Window owner ) method.

answered 2008-09-30T22:18:53.097

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