C# WinForm窗体绘制圆角

private void FormLogin_Paint(object sender, PaintEventArgs e)
        {
            Type(this, 20, 0.1);
           
        } 

 /// <summary>
        /// 圆角：radius=圆角弧度   rect是要做圆角的矩形
        /// </summary>
        public void SetWindowRegion(int width, int height)
        {
            System.Drawing.Drawing2D.GraphicsPath FormPath;
            FormPath = new System.Drawing.Drawing2D.GraphicsPath();
            Rectangle rect = new Rectangle(0, 0, width, height);
            FormPath = GetRoundedRectPath(rect, 8);
            this.Region = new Region(FormPath);
        }
        private GraphicsPath GetRoundedRectPath(Rectangle rect, int radius)
        {
            int diameter = radius;
            Rectangle arcRect = new Rectangle(rect.Location, new Size(diameter, diameter));
            GraphicsPath path = new GraphicsPath();
            //   左上角     
            path.AddArc(arcRect, 180, 90);
            //   右上角     
            arcRect.X = rect.Right - diameter;
            path.AddArc(arcRect, 270, 90);
            //   右下角     
            arcRect.Y = rect.Bottom - diameter;
            path.AddArc(arcRect, 0, 90);
            //   左下角     
            arcRect.X = rect.Left;
            path.AddArc(arcRect, 90, 90);
            path.CloseFigure();
            return path;
        }

        private void Type(Control sender, int p_1, double p_2)
        {
            GraphicsPath oPath = new GraphicsPath();
            oPath.AddClosedCurve(
                new Point[] {
            new Point(0, sender.Height / p_1),
            new Point(sender.Width / p_1, 0),
            new Point(sender.Width - sender.Width / p_1, 0),
            new Point(sender.Width, sender.Height / p_1),
            new Point(sender.Width, sender.Height - sender.Height / p_1),
            new Point(sender.Width - sender.Width / p_1, sender.Height),
            new Point(sender.Width / p_1, sender.Height),
            new Point(0, sender.Height - sender.Height / p_1) },

                (float)p_2);

            sender.Region = new Region(oPath);
        }