private void groupBox1_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.FillRectangle(Brushes.Transparent, e.ClipRectangle); 
            Rectangle Rtg_LT = new Rectangle();
            Rectangle Rtg_RT = new Rectangle();
            Rectangle Rtg_LB = new Rectangle();
            Rectangle Rtg_RB = new Rectangle();
            Rtg_LT.X = 0; Rtg_LT.Y = 7; Rtg_LT.Width = 10; Rtg_LT.Height = 10;
            Rtg_RT.X = e.ClipRectangle.Width - 11; Rtg_RT.Y = 7; Rtg_RT.Width = 10; Rtg_RT.Height = 10;
            Rtg_LB.X = 0; Rtg_LB.Y = e.ClipRectangle.Height - 11; Rtg_LB.Width = 10; Rtg_LB.Height = 10;
            Rtg_RB.X = e.ClipRectangle.Width - 11; Rtg_RB.Y = e.ClipRectangle.Height - 11; Rtg_RB.Width = 10; Rtg_RB.Height = 10;
            Color color = BorderColor;
            Pen Pen_AL = new Pen(color, 1);
            Pen_AL.Color = color;
            e.Graphics.DrawArc(Pen_AL, Rtg_LT, 180, 90);
            e.Graphics.DrawArc(Pen_AL, Rtg_RT, 270, 90);
            e.Graphics.DrawArc(Pen_AL, Rtg_LB, 90, 90);
            e.Graphics.DrawArc(Pen_AL, Rtg_RB, 0, 90);
            e.Graphics.DrawLine(Pen_AL, 5, 7, 6, 7);
            e.Graphics.DrawLine(Pen_AL, e.Graphics.MeasureString(groupBox1.Text, groupBox1.Font).Width + 3, 7, e.ClipRectangle.Width - 7, 7);
            e.Graphics.DrawLine(Pen_AL, 0, 13, 0, e.ClipRectangle.Height - 7);
            e.Graphics.DrawLine(Pen_AL, 6, e.ClipRectangle.Height - 1, e.ClipRectangle.Width - 7, e.ClipRectangle.Height - 1);
            e.Graphics.DrawLine(Pen_AL, e.ClipRectangle.Width - 1, e.ClipRectangle.Height - 7, e.ClipRectangle.Width - 1, 13);
        }

    class MyGroupBox:GroupBox
    {
        protected override void OnPaint(PaintEventArgs e)
        {
            using (Pen pen = new Pen(Color.SteelBlue))
            using (GraphicsPath path = new GraphicsPath())
            {
                Rectangle arc = new Rectangle(0, 7, 10, 10);
                path.AddArc(arc, 180, 90);
                arc.X = this.Width - arc.Width - 1;
                path.AddArc(arc, 270, 90);
                arc.Y = this.Height - arc.Height - 1;
                path.AddArc(arc, 0, 90);
                arc.X = 0;
                path.AddArc(arc, 90, 90);

                path.CloseFigure();

                e.Graphics.DrawPath(pen, path);
            }

            TextRenderer.DrawText(e.Graphics, this.Text, this.Font, new Point(7, 1), this.ForeColor, this.BackColor);
        }
    }