Get Image of Open Form

//necessary function to create bitmap of form

        [DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]

        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("user32.dll", ExactSpelling = true)]

        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll", ExactSpelling = true)]

        public static extern IntPtr BitBlt(IntPtr hDestDC, int x, int y,

             int nWidth, int nHeight, IntPtr hSrcDC,

             int xSrc, int ySrc, int dwRop);

        public static Bitmap GetFormImage(System.Windows.Forms.Form frm)

        {

            Graphics g = frm.CreateGraphics();

            Size s = frm.Size;

            Bitmap formImage = new Bitmap(s.Width, s.Height, g);

            Graphics mg = Graphics.FromImage(formImage);

            IntPtr dc1 = g.GetHdc();

            IntPtr dc2 = mg.GetHdc();

            BitBlt(dc2, 0, 0, frm.ClientRectangle.Width, frm.ClientRectangle.Height, dc1, 0, 0, 13369376);

            g.ReleaseHdc(dc1);

            mg.ReleaseHdc(dc2);

            return formImage;

        }