How do I set focus to an external application?

[HaLo2FrEeEk]

I've tried

[DllImport("User32.dll")]
private static extern IntPtr SetFocus(HandleRef hWnd);

And it's not wanting to work. I've tried passing both the process handle and the main window handle to the method with this code

SetFocus(new HandleRef(null, Process.MainWindowHandle));

And it just won't do it. I know I have the right handle because I'm using GetWindowRect() to get the size and location of the window, so why can't I set it's focus?

[Curtis Rutland]

Use SetForegroundWindow.

[HaLo2FrEeEk]

Ok that works, but only if the window in question is not minimized. Is there a way to detect the windowstate of an external application? I'm looking at GetWindowInfo(), but it returns a WINDOWINFO object and I don't know how to get at that.