ScreenCapture class

    public static class ScreenCapture
    {
        public static Bitmap Fullscreen()
        {
            using (Bitmap bm = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height))
            {
                using (Graphics g = Graphics.FromImage(bm))
                {
                    g.CopyFromScreen(Point.Empty, Point.Empty, Screen.PrimaryScreen.Bounds.Size);
                }

                return bm;
            }
        }
    }