应该是windowsForms吧。

下面是绘一个矩形：

Graphics g = panel1.CreateGraphics();
 Pen pen = new Pen(Brushes.Red,3);
Rectangle r=new Rectangle();
            r.Width=r.Height=200;
            r.Location = new Point(2, 2);
            g.DrawRectangle(pen,r);

其中pen中的3决定线条的粗细。

放一个几个pictureBox控件，控件中分别放一个图

点击每个pictureBox，产生pictureBox1_Click事件，根据每张图片的显示，为pen的第二个参数赋值。

每次赋值后别忘了刷新。

            Graphics g;
            Pen pen = new Pen(Brushes.Red,8);
           Rectangle r=new Rectangle();
        private void button1_Click(object sender, EventArgs e)
        {
            pen.Width = 1;
            huitu();

        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {
            pen.Width = 1;
            huitu();
        }
        public void huitu()
        {
            g = panel1.CreateGraphics();
            r.Width = r.Height = 200;
            r.Location = new Point(2, 2);
            g.DrawRectangle(pen, r);
        }