增加窗体边框3D效果

 /// <summary>
        /// 增加窗体边框3D效果
        /// </summary>
        /// <param name="e"></param>
        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            using (Pen bluePen = new Pen(Color.FromArgb(, , )))
            {
                e.Graphics.DrawLine(bluePen, , , this.Width - , );
                e.Graphics.DrawLine(bluePen, , , , this.Height - );
                e.Graphics.DrawLine(bluePen, , this.Height - , this.Width - , this.Height - );
                e.Graphics.DrawLine(bluePen, this.Width - , , this.Width - , this.Height - );
            }
        }