Ajax校验验证码（可以设置为数字、字母、中文汉字等，背景图有干扰线）

一般处理程序，获得验证码

    /// <summary>    /// VCode 的摘要说明    /// </summary>    public class VCode : IHttpHandler,System.Web.SessionState.IRequiresSessionState    {        public void ProcessRequest(HttpContext context)        {            //System.Threading.Thread.Sleep(5000);            context.Response.ContentType = "image/jpeg";            string code = GetRndNumStr();            //string code = GetRndNum();            //string code = GetRndStr();            //string code = GetRndCh();            context.Session["VCode"] = code;            using (Bitmap img = CreateImages(code, "ch"))            {                img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);            }        }        // 数字+字母随机        private string GetRndNumStr()        {            string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9";            string[] VcArray = Vchar.Split(',');            string checkCode = string.Empty;            Random rand = new Random();            for (int i = 0; i < 4; i++)            {                int t = rand.Next(VcArray.Length);                checkCode += VcArray[t];            }            return checkCode;        }        // 数字随机数        private string GetRndNum()        {            string code = string.Empty;            Random random = new Random();            for (int i = 0; i < 4; i++)            {                code += random.Next(9);            }            return code;        }        // 英文随机        private string GetRndStr()        {            string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";            string[] VcArray = Vchar.Split(',');            string checkCode = string.Empty;            Random rand = new Random();            for (int i = 0; i < 4; i++)            {                int t = rand.Next(VcArray.Length);                checkCode += VcArray[t];            }            return checkCode;        }        // 中文随机        private string GetRndCh()        {            System.Text.Encoding gb = System.Text.Encoding.Default;//获取GB2312编码页（表）            object[] bytes = CreateRegionCode(4);//生4个随机中文汉字编码            string[] str = new string[4];            System.Text.StringBuilder sb = new System.Text.StringBuilder();            for (int i = 0; i < 4; i++)            {                //根据汉字编码的字节数组解码出中文汉字                str[i] = gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));                sb.Append(str[i].ToString());            }            return sb.ToString();        }        // 产生随机中文字符        private static object[] CreateRegionCode(int strlength)        {            //定义一个字符串数组储存汉字编码的组成元素            string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };            Random rnd = new Random();            object[] bytes = new object[strlength];            for (int i = 0; i < strlength; i++)            {                //区位码第1位                int r1 = rnd.Next(11, 14);                string str_r1 = rBase[r1].Trim();                //区位码第2位                rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);                int r2;                if (r1 == 13)                {                    r2 = rnd.Next(0, 7);                }                else                {                    r2 = rnd.Next(0, 16);                }                string str_r2 = rBase[r2].Trim();                //区位码第3位                rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机种子                int r3 = rnd.Next(10, 16);                string str_r3 = rBase[r3].Trim();                //区位码第4位                rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);                int r4;                if (r3 == 10)                {                    r4 = rnd.Next(1, 16);                }                else if (r3 == 15)                {                    r4 = rnd.Next(0, 15);                }                else                {                    r4 = rnd.Next(0, 16);                }                string str_r4 = rBase[r4].Trim();                //定义两个字节变量存储产生的随机汉字区位码                byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);                byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);                //将两个字节变量存储在字节数组中                byte[] str_r = new byte[] { byte1, byte2 };                //将产生的一个汉字的字节数组放入object数组中                bytes.SetValue(str_r, i);            }            return bytes;        }        // 画图片的背景图+干扰线         private Bitmap CreateImages(string checkCode, string type)        {            int step = 0;            if (type == "ch")            {                step = 5;//中文字符，边界值做大            }            int iwidth = (int)(checkCode.Length * (13 + step));            System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 22);            Graphics g = Graphics.FromImage(image);            g.Clear(Color.White);//清除背景色            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };//定义随机颜色            string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };            Random rand = new Random();            for (int i = 0; i < 50; i++)            {                int x1 = rand.Next(image.Width);                int x2 = rand.Next(image.Width);                int y1 = rand.Next(image.Height);                int y2 = rand.Next(image.Height);                g.DrawLine(new Pen(Color.LightGray, 1), x1, y1, x2, y2);//根据坐标画线            }            for (int i = 0; i < checkCode.Length; i++)            {                int cindex = rand.Next(7);                int findex = rand.Next(5);                Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);                Brush b = new System.Drawing.SolidBrush(c[cindex]);                int ii = 4;                if ((i + 1) % 2 == 0)                {                    ii = 2;                }                g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * (12 + step)), ii);            }            g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);            System.IO.MemoryStream ms = new System.IO.MemoryStream();            return image;        }        public bool IsReusable        {            get            {                return false;            }        }    }

HTML代码

    验证码:    <input id="txtVcode" type="text" />    <img alt="" id="imgCode" src="/js/vcode/VCode.ashx" />    <a id="aCode" href="javascript:void(0)">看不清，换一张</a>    <div id="txtVcodeTip"></div>

Javascript变换验证码代码

function getVCode() {    $("#imgCode").attr("src", "/js/vcode/VCode.ashx?r=" + new Date());}$(function () {    //验证码    var imgCode = $("#imgCode");    imgCode.attr("alt", "点击获取验证码");    imgCode.attr("title", "点击更换验证码");    imgCode.css("cursor", "pointer");    imgCode.click(function () {//点击验证码本身切换验证码        getVCode();    });    //点击文字超链接更换验证码    var aCode = $("#aCode");    aCode.click(function () {        getVCode();    });    //验证码提示消息    var vcodeMsg = $("#txtVcodeTip");    vcodeMsg.css("color", "Red");    var vcode = $("#txtVcode");    vcode.blur(function () {        if ($.trim(vcode.val()) == '') {            vcodeMsg.text("验证码不能为空");            return false;        } else {            $.post("/js/vcode/CheckVCode.ashx", { "vcode": $.trim(vcode.val()) }, function (data) {                vcodeMsg.text(data);            });        }    }).focus(function () {        vcodeMsg.text("");    });});

CheckVCode.ashx代码

    public class CheckVCode : IHttpHandler, System.Web.SessionState.IRequiresSessionState    {        public void ProcessRequest(HttpContext context)        {            context.Response.ContentType = "text/plain";            string vcode = context.Request["vcode"];            context.Response.Write(CheckCode(vcode));        }        public static string CheckCode(string vcode)        {            if (HttpContext.Current.Session["VCode"] != null)            {                string sysCode = HttpContext.Current.Session["VCode"].ToString();                //使用  Compare  方法，这个方法可以做大小写忽略的比较，并且不会创建新字符串                if (String.Compare(vcode, sysCode, true) == 0)                {                    return "ok";                }                else                {                    return "验证码输入错误,重新输入";                }            }            else            {                return "验证码过期，请更换验证码";            }        }        public bool IsReusable        {            get            {                return false;            }        }    }