public void SetWindowRegion()
{System.Drawing.Drawing2D.GraphicsPath FormPath;FormPath = new System.Drawing.Drawing2D.GraphicsPath();Rectangle rect = new Rectangle(0, 22, this.Width, this.Height - 22);//this.Left-10,this.Top-10,this.Width-10,this.Height-10);FormPath = GetRoundedRectPath(rect, 10);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;
}protected override void OnResize(System.EventArgs e)
{this.Region = null;SetWindowRegion();
}

private SetFormCircle()
{int radian = 4; //圆弧角的比率，可以自己改变这个值看具体的效果int w = this.Width; //窗体宽int h = this.Height; //窗体高//对于矩形的窗体，要在一个角上画个弧度至少需要2个点，所以4个角需要至少8个点Point p1 = new Point(radian, 0);Point p2 = new Point(w - radian, 0);Point p3 = new Point(w, radian);Point p4 = new Point(w, h - radian);Point p5 = new Point(w - radian, h);Point p6 = new Point(radian, h);Point p7 = new Point(0, h - radian);Point p8 = new Point(0, radian);System.Drawing.Drawing2D.GraphicsPath shape = new System.Drawing.Drawing2D.GraphicsPath();Point[] p = new Point[] { p1, p2, p3, p4, p5, p6, p7, p8 };shape.AddPolygon(p);//将窗体的显示区域设为GraphicsPath的实例this.Region = new System.Drawing.Region(shape);
}
private void Form1_Load(object sender, EventArgs e)
{SetFormCircle();
}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);
}
//备注：在窗体的paint和resize事件中增加:Type(this,20,0.1);
//(参数20和0.1也可以根据自己的需要调整到最佳效果)