private void panel1_Paint(object sender, PaintEventArgs e)
        {
                Pen p = new Pen(Brushes.Black, 2);
                e.Graphics.DrawRectangle(p, e.ClipRectangle);
        }

        private void panel1_SizeChanged(object sender, EventArgs e)
        {
            Graphics gr = panel1.CreateGraphics();
            Pen pen1 = new Pen(Color.Black);
            panel1.Refresh();
        }