小弟初学,哪位大哥给源代码学习学习.

选中窗体Form1 ,找到MouseDown事件,双击,然后填写下面的语句就可以了

 private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            Graphics g = Graphics.FromHwnd(this.Handle);   
            g.DrawLine(new Pen(Color.Red),new Point(e.X,e.Y),new Point(e.X+1, e.Y));
        }