验证码

 protected void Page_Load(object sender, EventArgs e)
    {
        List<Color> clist = new List<Color>();
        clist.Add(Color.Red);
        clist.Add(Color.Firebrick);
        clist.Add(Color.LawnGreen);
        clist.Add(Color.Goldenrod);
        clist.Add(Color.Cyan);
        clist.Add(Color.DarkSlateBlue);
        clist.Add(Color.Indigo);
        Random r = new Random();
        string s = "";
        string all = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmeopqrstuvwxyz0123456789";
        for (int i = 0; i < 4; i++)
        {
            s += all.Substring(r.Next(0, all.Length), 1);
        }

        Session["YZM"] = s;

        Bitmap img = new Bitmap(120, 60);

        Graphics g2 = Graphics.FromImage(img);
        Brush b2 = new SolidBrush(clist[r.Next(0, clist.Count)]);
        g2.FillRectangle(b2, 0, 0, 120, 60);

        Graphics g = Graphics.FromImage(img);
        Font f = new Font("微软雅黑", 30);
        Brush b = new SolidBrush(Color.Red);

        g.DrawString(s, f, b, new PointF(0, 0));


        for (int i = 0; i < 8; i++)
        {
            Graphics g3 = Graphics.FromImage(img);
            Pen p3 = new Pen(new SolidBrush(clist[r.Next(0, clist.Count)]), r.Next(2, 5));
            g3.DrawLine(p3, new Point(r.Next(0, 120), r.Next(0, 60)), new Point(r.Next(0, 120), r.Next(0, 60)));
        }


        img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png);



    }