ASP.NET产生随机验证码

 protected void Page_Load(object sender, EventArgs e)    {        //用来保存随机字符串        string chkCode = string.Empty;        //字体的颜色        Color[] color = new Color[] {Color.Black,Color.Red,Color.Blue,Color.Green,        Color.Brown,Color.DarkBlue,Color.Gray};        //字体        string[] font = new string[]{"Times New Roman","MS Mincho","Book Antiqua",         "Gungsuh", "PMingLiU", "Impact"};        //字符串集合        char[] character = new char[] { '2', '3', '4', '5', '6', '8', '9', 'A', 'B',             'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };        //Random用来产生随机数        Random rd = new Random();        for (int i = 0; i < 4;i++ )        {            chkCode += character[rd.Next(character.Length)]; //随机产生一个字母，最后组成验证码        }        //定义一副位图        Bitmap bmp = new Bitmap(100, 40); //指定大小        //创建画布，来自位图bmp        Graphics g = Graphics.FromImage(bmp);        g.Clear(Color.White);        //画线        for (int i = 0; i < 10;i++ )        {            int x1 = rd.Next(100); //随机产生点的位置            int y1 = rd.Next(40);            int x2 = rd.Next(100);            int y2 = rd.Next(40);            Color clr=color[rd.Next(color.Length)]; //随机产生一种线的颜色            g.DrawLine(new Pen(clr), x1, y1, x2, y2);        }        //画验证码        for (int i = 0; i < chkCode.Length;i++ )        {            string fnt = font[rd.Next(font.Length)]; //随机产生一种字体            Font ft = new Font(fnt, 18);            Color clr = color[rd.Next(color.Length)]; //随机产生一种颜色            g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), i * 20 + 8, 8);        }        //画点        for (int i = 0; i < 100;i++ )        {            int x = rd.Next(bmp.Width); //随机产生点            int y = rd.Next(bmp.Height);            Color clr = color[rd.Next(color.Length)]; //随机产生颜色            bmp.SetPixel(x, y, clr);        }        Response.Buffer = true;        Response.ExpiresAbsolute = DateTime.Now.AddMilliseconds(0);        Response.Expires = 0;        Response.CacheControl = "no-cache";        Response.AppendHeader("Pragma", "No-Cache");        MemoryStream ms = new MemoryStream(); //定义一个内存流对象        try        {            bmp.Save(ms, ImageFormat.Png); //将图像以指定的格式保存到内存流中            Response.ClearContent();            Response.ContentType = "image/png"; //设置HTTP输出流的类型            Response.BinaryWrite(ms.ToArray()); //将字节写入输出流        }        finally        {            //释放资源            bmp.Dispose();            g.Dispose();        }    }

使用时将img的src设置为产生验证码文件的路径即可。

<asp:Image ID="Image1" runat="server" src="shengchengYZM.aspx" />

<a href="Login.aspx">看不清，换一张</a>

如果要实现点击图片也能更新验证码的话，可以在image的onclick加上onclick="this.src='shengchengYZM.aspx?a='+new Date().getMilliseconds()" 。即让每次点击都请求新的图片。

注：本文转自 http://www.jb51.net/article/9492.htm