Web验证码的使用

1、首先，在项目中新建一个“Tools”的文件夹，然后在文件夹中建一个“verify_code.ashx”的页面，注意该页面中有一个将验证码写入Seeion和Cookie的操作：

该验证码方法来自网上代码：

using System;using System.IO;using System.Drawing;using System.Drawing.Imaging;using System.Web;using System.Web.SessionState;namespace DT.Web.tools{    /// <summary>    /// 验证码生成类    /// </summary>    public class verify_code : IHttpHandler, IRequiresSessionState    {        public void ProcessRequest(HttpContext context)        {            int codeW = 80;            int codeH = 22;            int fontSize = 16;            string chkCode = string.Empty;            //颜色列表，用于验证码、噪线、噪点             Color[] color = { Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };            //字体列表，用于验证码             string[] font = { "Times New Roman", "Verdana", "Arial", "Gungsuh", "Impact" };            //验证码的字符集，去掉了一些容易混淆的字符             char[] character = { '2', '3', '4', '5', '6', '8', '9', 'a', 'b', 'd', 'e', 'f', 'h', 'k', 'm', 'n', 'r', 'x', 'y', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };            Random rnd = new Random();            //生成验证码字符串             for (int i = 0; i < 4; i++)            {                chkCode += character[rnd.Next(character.Length)];            }            //写入Session或者Cookie            context.Session["dt_session_code"] = chkCode;            context.Response.Cookies["dt_session_code"].Value = chkCode;             //创建画布            Bitmap bmp = new Bitmap(codeW, codeH);            Graphics g = Graphics.FromImage(bmp);            g.Clear(Color.White);            //画噪线             for (int i = 0; i < 1; i++)            {                int x1 = rnd.Next(codeW);                int y1 = rnd.Next(codeH);                int x2 = rnd.Next(codeW);                int y2 = rnd.Next(codeH);                Color clr = color[rnd.Next(color.Length)];                g.DrawLine(new Pen(clr), x1, y1, x2, y2);            }            //画验证码字符串             for (int i = 0; i < chkCode.Length; i++)            {                string fnt = font[rnd.Next(font.Length)];                Font ft = new Font(fnt, fontSize);                Color clr = color[rnd.Next(color.Length)];                g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 18 + 2, (float)0);            }            //画噪点             for (int i = 0; i < 100; i++)            {                int x = rnd.Next(bmp.Width);                int y = rnd.Next(bmp.Height);                Color clr = color[rnd.Next(color.Length)];                bmp.SetPixel(x, y, clr);            }            //清除该页输出缓存，设置该页无缓存             context.Response.Buffer = true;            context.Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);            context.Response.Expires = 0;            context.Response.CacheControl = "no-cache";            context.Response.AppendHeader("Pragma", "No-Cache");            //将验证码图片写入内存流，并将其以 "image/Png" 格式输出             MemoryStream ms = new MemoryStream();            try            {                bmp.Save(ms, ImageFormat.Png);                context.Response.ClearContent();                context.Response.ContentType = "image/Png";                context.Response.BinaryWrite(ms.ToArray());            }            finally            {                //显式释放资源                 bmp.Dispose();                g.Dispose();            }        }        public bool IsReusable        {            get            {                return false;            }        }    }}

2、新建一个HTML的页面，调用验证码：

 <div>   <input id="vierfiy" type="text"/>   <a onclick="ToggleCode(this, '/Tools/verify_code.ashx');return false;" href="javascript:;" title="点击切换验证码">    <img width="80" height="22" src="/Tools/verify_code.ashx?time=0.651968694964577"></img></a>       <input id="submit" type="button" value="提交"  onclick="SumbitVierfiy()"/></div><script>        //切换验证码        function ToggleCode(obj, codeurl) {            $(obj).children("img").eq(0).attr("src", codeurl + "?time=" + Math.random());            return false;        }        //提交验证码        function SumbitVierfiy() {            var code = readCookie('dt_session_code').toLowerCase();            var verfiyText = $("#vierfiy").val();            if (verfiyText != code)                alert("您输入的验证码与系统的不一致！");            else                alert("输入成功！");        }        //读取Cookie        function readCookie(name) {            var cookieValue = "";            var search = name + "=";            if (document.cookie.length > 0) {                var offset = document.cookie.indexOf(search);                if (offset != -1) {                    offset += search.length;                    end = document.cookie.indexOf(";", offset);                    if (end == -1) end = document.cookie.length;                    cookieValue = unescape(document.cookie.substring(offset, end));                }            }            return cookieValue;        }    </script>

效果如下：