Show a Form without stealing focus?

Question

Hmmm, isn't simply overriding Form.ShowWithoutActivation enough?

protected override bool ShowWithoutActivation
{
  get { return true; }
}

And if you don't want the user to click this notification window either, you can override CreateParams:

protected override CreateParams CreateParams
{
  get
  {
    CreateParams baseParams = base.CreateParams;

    const int WS_EX_NOACTIVATE = 0x08000000;
    const int WS_EX_TOOLWINDOW = 0x00000080;
    baseParams.ExStyle |= ( int )( WS_EX_NOACTIVATE | WS_EX_TOOLWINDOW );

    return baseParams;
  }
}

Stolen from PInvoke.net's ShowWindow method:

private const int SW_SHOWNOACTIVATE = 4;
private const int HWND_TOPMOST = -1;
private const uint SWP_NOACTIVATE = 0x0010;

[DllImport("user32.dll", EntryPoint = "SetWindowPos")]
static extern bool SetWindowPos(
     int hWnd,             // Window handle
     int hWndInsertAfter,  // Placement-order handle
     int X,                // Horizontal position
     int Y,                // Vertical position
     int cx,               // Width
     int cy,               // Height
     uint uFlags);         // Window positioning flags

[DllImport("user32.dll")]
static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

static void ShowInactiveTopmost(Form frm)
{
     ShowWindow(frm.Handle, SW_SHOWNOACTIVATE);
     SetWindowPos(frm.Handle.ToInt32(), HWND_TOPMOST,
     frm.Left, frm.Top, frm.Width, frm.Height,
     SWP_NOACTIVATE);
}

(Alex Lyman answered this, I'm just expanding it by directly pasting the code. Someone with edit rights can copy it over there and delete this for all I care ;) )

If you're willing to use Win32 P/Invoke, then you can use the ShowWindow method (the first code sample does exactly what you want).

This is what worked for me. It provides TopMost but without focus-stealing.

    protected override bool ShowWithoutActivation
    {
       get { return true; }
    }

    private const int WS_EX_TOPMOST = 0x00000008;
    protected override CreateParams CreateParams
    {
       get
       {
          CreateParams createParams = base.CreateParams;
          createParams.ExStyle |= WS_EX_TOPMOST;
          return createParams;
       }
    }

Remember to omit setting TopMost in Visual Studio designer, or elsewhere.

This is stolen, err, borrowed, from here (click on Workarounds):

https://connect.microsoft.com/VisualStudio/feedback/details/401311/showwithoutactivation-is-not-supported-with-topmost