Graphics g = e.Graphics;
Pen solidPen = new Pen(Color.Black, 4);
Pen dshPen = new Pen(Color.Blue);
dshPen.DashStyle = DashStyle.Solid;
Point[] points2 ={ new Point(10, 10), new Point(80, 20), new Point(130, 160), new Point(60, 160), new Point(5, 80) };
g.DrawPolygon(solidPen, points2);
GraphicsPath path = new GraphicsPath();
path.AddPolygon(points2);
path.CloseFigure();
Region region = new Region(path);
SolidBrush solidbrush = new SolidBrush(Color.Black);
g.FillRegion(solidbrush, region);
Point point = new Point(1, 1);
if (region.IsVisible(point, e.Graphics))
MessageBox.Show ("在区域内");