class{
  private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            SolidBrush brush = new SolidBrush(Color.DarkRed);
            Pen pen = new Pen(brush);
            foreach (Point pt in breakPointList)
         {
                g.DrawEllipse(new Pen(brush), pt.X-6, pt.Y-6, 12, 12);
                g.FillEllipse(brush, pt.X - 6, pt.Y - 6, 12, 12);
         }
        }

        List<Point> breakPointList = new List<Point>();

        private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
            breakPointList.Add(new Point(e.X, e.Y));
            this.pictureBox1.Refresh();  //引发Paint 函数
        }
}