Проверка, находиться ли компьютер в полноэкранном режиме - C#

   class FullSceen
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }
        [DllImport("user32.dll")]
        private static extern IntPtr GetForegroundWindow();
        [DllImport("user32.dll")]
        private static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        private static extern IntPtr GetShellWindow();
        [DllImport("user32.dll", SetLastError = true)]
        private static extern int GetWindowRect(IntPtr hwnd, out RECT rc);
        private IntPtr desktopHandle; //Window handle for the desktop
        private IntPtr shellHandle; //Window handle for the shell
        //Get the handles for the desktop and shell now.
        public bool isfull()
        {
            desktopHandle = GetDesktopWindow();
            shellHandle = GetShellWindow();
 
            bool runningFullScreen = false;
            RECT appBounds;
            Rectangle screenBounds;
            IntPtr hWnd;
 
            //get the dimensions of the active window
            hWnd = GetForegroundWindow();
            if (hWnd != null && !hWnd.Equals(IntPtr.Zero))
            {
                //Check we haven't picked up the desktop or the shell
                if (!(hWnd.Equals(desktopHandle) || hWnd.Equals(shellHandle)))
                {
                    GetWindowRect(hWnd, out appBounds);
                    //determine if window is fullscreen
                    screenBounds = Screen.FromHandle(hWnd).Bounds;
                    if ((appBounds.Bottom - appBounds.Top) == screenBounds.Height && (appBounds.Right - appBounds.Left) == screenBounds.Width)
                    {
                        runningFullScreen = true;
                    }
                }
            }
 
            return (runningFullScreen);
        }
    }