this.CreateGraphics().DrawLine(Pens.Black, new Point(100, 100), new Point(200, 200));
            this.Refresh();
            GraphicsPath gp = new GraphicsPath();
            List<PointF> arrPoints = new List<PointF>();
            arrPoints.Add(new PointF(0, 0));
            arrPoints.Add(new PointF(100, 0));
            arrPoints.Add(new PointF(100, 100));
            gp.AddLines(arrPoints.ToArray());
            gp.CloseFigure();
            this.CreateGraphics().DrawPath(Pens.Black, gp);
            Region r = new Region(gp);
            button1.Region = r;
            button1.BackColor = Color.Red;

------解决方案--------------------

C# code

            GraphicsPath gp = new GraphicsPath();
            List<PointF> arrPoints = new List<PointF>();
            arrPoints.Add(new PointF(0, 0));
            arrPoints.Add(new PointF(100, 0));
            arrPoints.Add(new PointF(100, 100));
            gp.AddLines(arrPoints.ToArray());
            gp.CloseFigure();
            this.CreateGraphics().DrawPath(Pens.Black, gp);
            Region r = new Region(gp);
            button1.Region = r;
            button1.BackColor = Color.Red;