验证码的使用

//在一个页面做上面版，进行绘画

//随机获得五位数
            string[] code = { "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "a", "b", "c", "d", "e", "f", "g", "h", "i", "g", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G", "H", "I", "G", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
            string pp = "";
            Random rd = new Random();
            for (int i = 0; i < 4; i++)
            {
                pp += code[rd.Next(0, 61)];
            }

            StaticData.code = pp;
            //构造面板
            Bitmap bt = new Bitmap(80, 30);  //定义一个面板
            Graphics gp = Graphics.FromImage(bt);   //在面板上定义绘图的实例
            Rectangle rc = new Rectangle(2, 2, 76, 26);    //定义一个矩形
            gp.FillRectangle(new SolidBrush(Color.Green), rc);    //填充矩形
            gp.DrawString(pp, new Font("幼圆", 20), new SolidBrush(Color.Blue), rc);  //在矩形中画出字符串

            Pen p = new Pen(Color.White, 1);
            //Point p1 = new Point(2, 2);
            //Point p2 = new Point(76, 76);
            //gp.DrawLine(p, p1, p2);
            for (int i = 0; i < 5; i++)
            {
                int x1 = rd.Next(80);
                int y1 = rd.Next(30);
                int x2 = rd.Next(80);
                int y2 = rd.Next(30);
                Point p1 = new Point(x1, y1);
                Point p2 = new Point(x2, y2);
                gp.DrawLine(p, p1, p2);
            }


            bt.Save(Response.OutputStream, ImageFormat.Jpeg);   //将图片显示出来

//在页面应用

<img src="../yanzheng.aspx" onclick="news()" runat="server" id="img" />

//JS代码实现点击刷新

function news() {
            var myDate = new Date();
            var id = document.getElementById("img");
            id.src = "ImgCode.aspx?"+myDate.toLocaleString();
        }