例一：

在网站要目录下添加ValidateCode.aspx,路径自己定。

ValidateCode.aspx：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ValidateCode.aspx.cs" Inherits="ValidateCode_ValidateCode" %>

 ValidateCode.aspx.cs：

using System;using System.Collections.Generic;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;using System.IO;using System.Drawing.Imaging;public partial class ValidateCode_ValidateCode : System.Web.UI.Page{    private int letterWidth = 15;//单个字体的宽度范围    private int letterHeight = 27;//单个字体的高度范围    private int letterCount = 5;//验证码位数    private char[] chars = "23456789QWERTYUPASDFGHJKLZXCVBNMqwertyupasdfghjkzxcvbnm".ToCharArray();    private string[] fonts = { "Arial", "Georgia" };    /// 
    /// 产生波形滤镜效果    /// 
    private const double PI = 3.1415926535897932384626433832795;    private const double PI2 = 6.283185307179586476925286766559;    protected void Page_Load(object sender, EventArgs e) {        //防止网页后退--禁止缓存            Response.Expires = 0;        Response.Buffer = true;        Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);        Response.AddHeader("pragma", "no-cache");        Response.CacheControl = "no-cache";        string str_ValidateCode = GetRandomNumberString(letterCount);        HttpCookie objCookie = new HttpCookie("ValidateCode");        objCookie.Value = str_ValidateCode.ToLower();        objCookie.Path = "/";        objCookie.Expires = DateTime.Now.AddSeconds(1200);        Response.Cookies.Add(objCookie);        CreateImage(str_ValidateCode);    }    public void CreateImage(string checkCode) {        int int_ImageWidth = checkCode.Length * letterWidth + 5;        Random newRandom = new Random();        Bitmap image = new Bitmap(int_ImageWidth, letterHeight);        Graphics g = Graphics.FromImage(image);        //生成随机生成器        Random random = new Random();        //白色背景        g.Clear(Color.White);        //画图片的背景噪音线        for (int i = 0; i < 10; i++) {            int x1 = random.Next(image.Width);            int x2 = random.Next(image.Width);            int y1 = random.Next(image.Height);            int y2 = random.Next(image.Height);            g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);        }        //画图片的前景噪音点        for (int i = 0; i < 10; i++) {            int x = random.Next(image.Width);            int y = random.Next(image.Height);            image.SetPixel(x, y, Color.FromArgb(random.Next()));        }        //随机字体和颜色的验证码字符        int findex;        for (int int_index = 0; int_index < checkCode.Length; int_index++) {            findex = newRandom.Next(fonts.Length - 1);            string str_char = checkCode.Substring(int_index, 1);            Brush newBrush = new SolidBrush(GetRandomColor());            Point thePos = new Point(int_index * letterWidth + 1 + newRandom.Next(3), 1 + newRandom.Next(3));//5+1+a+s+p+x            g.DrawString(str_char, new Font(fonts[findex], 14, FontStyle.Bold), newBrush, thePos);        }        //灰色边框        g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));        //图片扭曲        //image = TwistImage(image, true, 3, 4);        //将生成的图片发回客户端        MemoryStream ms = new MemoryStream();        image.Save(ms, ImageFormat.Png);        Response.ClearContent(); //需要输出图象信息 要修改HTTP头         Response.ContentType = "image/Png";        Response.BinaryWrite(ms.ToArray());        g.Dispose();        image.Dispose();    }    /// 
    /// 正弦曲线Wave扭曲图片    /// 
    /// 图片路径    /// 如果扭曲则选择为True    /// 波形的幅度倍数，越大扭曲的程度越高，一般为3    /// 波形的起始相位，取值区间[0-2*PI)    /// 
          public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase) {        System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);        // 将位图背景填充为白色        System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);        graph.Dispose();        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;        for (int i = 0; i < destBmp.Width; i++) {            for (int j = 0; j < destBmp.Height; j++) {                double dx = 0;                dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;                dx += dPhase;                double dy = Math.Sin(dx);                // 取得当前点的颜色                int nOldX = 0, nOldY = 0;                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;                nOldY = bXDir ? j : j + (int)(dy * dMultValue);                System.Drawing.Color color = srcBmp.GetPixel(i, j);                if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height) {                    destBmp.SetPixel(nOldX, nOldY, color);                }            }        }        return destBmp;    }    public Color GetRandomColor() {        Random RandomNum_First = new Random((int)DateTime.Now.Ticks);        System.Threading.Thread.Sleep(RandomNum_First.Next(50));        Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);        int int_Red = RandomNum_First.Next(210);        int int_Green = RandomNum_Sencond.Next(180);        int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;        int_Blue = (int_Blue > 255) ? 255 : int_Blue;        return Color.FromArgb(int_Red, int_Green, int_Blue);    }    //  生成随机数字字符串    public string GetRandomNumberString(int int_NumberLength) {        Random random = new Random();        string validateCode = string.Empty;        for (int i = 0; i < int_NumberLength; i++)            validateCode += chars[random.Next(0, chars.Length)].ToString();        return validateCode;    }}

使用时：

放在页面前

<span>验证码：</span>

<input name="txtCode" runat="server" type="text" id="txtCode" class="txtinput1" />

<img class="txtverity" οnclick="this.src=this.src+'?'" src="ValidateCode/ValidateCode.aspx" style="cursor: pointer" alt="看不清楚，换一张" title="看不清楚，换一张" />

//οnclick="this.src='ValifyCode.aspx?r=' + Math.random();

放在页面后

protected void btnSendMsg_Click(object sender, EventArgs e) {

if (Request.Cookies["ValidateCode"] == null) {

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。')", true);

return;

}

else {

if (string.Compare(Request.Cookies["ValidateCode"].Value, txtCode.Value.Trim().ToLower(), true) == 0) {

insertMsgToUs();

}

else {

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('验证码不正确!')", true);

}

}

}

 

例二：

在网站根目录下添加自定义控件VerifyImage.ashx：

<%@ WebHandler Language="C#"  Class="VerifyImage" %>using System;using System.Data;using System.Configuration;using System.Collections;using System.Collections.Generic;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Drawing;    /// 
    /// 生成验证码    /// 
    public  class VerifyImage : IHttpHandler    {        public void ProcessRequest(HttpContext context)        {            context.Response.ContentType = "text/plain";            VerifyImage v = new VerifyImage();            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);//如不加，单击验证图片＇看不清换一张＇            v.Length = this.length;            v.FontSize = this.fontSize;            v.Chaos = this.chaos;            v.BackgroundColor = this.backgroundColor;            v.ChaosColor = this.chaosColor;            v.CodeSerial = this.codeSerial;            v.Colors = this.colors;            v.Fonts = this.fonts;            v.Padding = this.padding;            string code = v.CreateVerifyCode();        //取随机码            v.CreateImageOnPage(code, context);        // 输出图片            context.Response.Cookies.Add(new HttpCookie("VerifyCode", code.ToUpper()));// 使用Cookies取验证码的值        }        public bool IsReusable        {            get            {                return false;            }        }        #region 验证码长度(默认6个验证码的长度)        int length = 5;        public int Length        {            get { return length; }            set { length = value; }        }        #endregion        #region 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)        int fontSize = 12;        public int FontSize        {            get { return fontSize; }            set { fontSize = value; }        }        #endregion        #region 边框补(默认1像素)        int padding = 2;        public int Padding        {            get { return padding; }            set { padding = value; }        }        #endregion        #region 是否输出燥点(默认不输出)        bool chaos = true;        public bool Chaos        {            get { return chaos; }            set { chaos = value; }        }        #endregion        #region 输出燥点的颜色(默认灰色)        Color chaosColor = Color.LightGray;        public Color ChaosColor        {            get { return chaosColor; }            set { chaosColor = value; }        }        #endregion        #region 自定义背景色(默认白色)        Color backgroundColor = Color.White;        public Color BackgroundColor        {            get { return backgroundColor; }            set { backgroundColor = value; }        }        #endregion        #region 自定义随机颜色数组        Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };        public Color[] Colors        {            get { return colors; }            set { colors = value; }        }        #endregion        #region 自定义字体数组        string[] fonts = { "Arial", "Georgia" };        public string[] Fonts        {            get { return fonts; }            set { fonts = value; }        }        #endregion        #region 自定义随机码字符串序列(使用逗号分隔)        string codeSerial = "1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";        public string CodeSerial        {            get { return codeSerial; }            set { codeSerial = value; }        }        #endregion        #region 产生波形滤镜效果        private const double PI = 3.1415926535897932384626433832795;        private const double PI2 = 6.283185307179586476925286766559;        /// 
        /// 正弦曲线Wave扭曲图片        /// 
        /// 图片路径        /// 如果扭曲则选择为True        /// 波形的幅度倍数，越大扭曲的程度越高，一般为3        /// 波形的起始相位，取值区间[0-2*PI)        /// 
              public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)        {            System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);            // 将位图背景填充为白色            System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);            graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);            graph.Dispose();            double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;            for (int i = 0; i < destBmp.Width; i++)            {                for (int j = 0; j < destBmp.Height; j++)                {                    double dx = 0;                    dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;                    dx += dPhase;                    double dy = Math.Sin(dx);                    // 取得当前点的颜色                    int nOldX = 0, nOldY = 0;                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);                    System.Drawing.Color color = srcBmp.GetPixel(i, j);                    if (nOldX >= 0 && nOldX < destBmp.Width                     && nOldY >= 0 && nOldY < destBmp.Height)                    {                        destBmp.SetPixel(nOldX, nOldY, color);                    }                }            }            return destBmp;        }        #endregion        #region 生成校验码图片        public Bitmap CreateImageCode(string code)        {            int fSize = FontSize;            int fWidth = fSize + Padding;            int imageWidth = (int)(code.Length * fWidth) + 4 + Padding * 2;            int imageHeight = fSize * 2 + Padding;            System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageWidth, imageHeight);            Graphics g = Graphics.FromImage(image);            g.Clear(BackgroundColor);            Random rand = new Random();            //给背景添加随机生成的燥点            if (this.Chaos)            {                Pen pen = new Pen(ChaosColor, 0);                int c = Length * 10;                for (int i = 0; i < c; i++)                {                    int x = rand.Next(image.Width);                    int y = rand.Next(image.Height);                    g.DrawRectangle(pen, x, y, 1, 1);                }            }            int left = 0, top = 0, top1 = 1, top2 = 1;            int n1 = (imageHeight - FontSize - Padding * 2);            int n2 = n1 / 4;            top1 = n2;            top2 = n2 * 2;            Font f;            Brush b;            int cindex, findex;            //随机字体和颜色的验证码字符            for (int i = 0; i < code.Length; i++)            {                cindex = rand.Next(Colors.Length - 1);                findex = rand.Next(Fonts.Length - 1);                f = new System.Drawing.Font(Fonts[findex], fSize, System.Drawing.FontStyle.Bold);                b = new System.Drawing.SolidBrush(Colors[cindex]);                if (i % 2 == 1)                {                    top = top2;                }                else                {                    top = top1;                }                left = i * fWidth;                g.DrawString(code.Substring(i, 1), f, b, left, top);            }            //画一个边框 边框颜色为Color.Gainsboro            //g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1);            //g.Dispose();            //产生波形            //image = TwistImage(image, true, 8, 4);            image = TwistImage(image, true, 0, 0);            return image;        }        #endregion        #region 将创建好的图片输出到页面        public void CreateImageOnPage(string code, HttpContext context)        {            System.IO.MemoryStream ms = new System.IO.MemoryStream();            Bitmap image = this.CreateImageCode(code);            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);            context.Response.ClearContent();            context.Response.ContentType = "image/Jpeg";            context.Response.BinaryWrite(ms.GetBuffer());            ms.Close();            ms = null;            image.Dispose();            image = null;        }        #endregion        #region 生成随机字符码        public string CreateVerifyCode(int codeLen)        {            if (codeLen == 0)            {                codeLen = Length;            }            string[] arr = CodeSerial.Split(',');            string code = "";            int randValue = -1;            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < codeLen; i++)            {                randValue = rand.Next(0, arr.Length - 1);                code += arr[randValue];            }            return code;        }        public string CreateVerifyCode()        {            return CreateVerifyCode(0);        }        #endregion    }

使用时：

放在页面前

<span>验证码：</span>

<input name="txtCode" runat="server" type="text" id="txtCode" class="txtinput1" />

<img src="VerifyImage.ashx" class="txtverity" οnclick="this.src=this.src+'?'" alt="点击刷新验证码"/>

放在页面后

protected void btnSendMsg_Click(object sender, EventArgs e) {

if (Request.Cookies["VerifyCode"] == null) {

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。')", true);

return;

}

else {

if (string.Compare(Request.Cookies["VerifyCode"].Value, txtCode.Value.Trim().ToUpper(), true) == 0) {

insertMsgToUs();

}

else {

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('验证码不正确!')", true);

}

}

}

 

例三：

添加ValidateCode.aspx，

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;using System.Drawing.Imaging;using System.IO;public partial class ValidateCode : System.Web.UI.Page{    private void CreateImage(string checkCode)        {            int width = checkCode.Length * 14;            Bitmap image = new Bitmap(width, 20);            Graphics graphics = Graphics.FromImage(image);            Font font = new Font("Arial ", 10f);            Brush brush = new SolidBrush(Color.Black);            Brush brush2 = new SolidBrush(Color.FromArgb(0xa6, 8, 8));            graphics.Clear(ColorTranslator.FromHtml("#99C1CB"));            char[] chArray = checkCode.ToCharArray();            for (int i = 0; i < chArray.Length; i++)            {                if ((chArray[i] >= '0') && (chArray[i] <= '9'))                {                    graphics.DrawString(chArray[i].ToString(), font, brush2, (float) (3 + (i * 12)), 3f);                }                else                {                    graphics.DrawString(chArray[i].ToString(), font, brush, (float) (3 + (i * 12)), 3f);                }            }            MemoryStream stream = new MemoryStream();            image.Save(stream, ImageFormat.Jpeg);            base.Response.Cache.SetNoStore();            base.Response.ClearContent();            base.Response.ContentType = "image/Jpeg";            base.Response.BinaryWrite(stream.ToArray());            graphics.Dispose();            image.Dispose();        }        private string CreateRandomCode(int codeCount)        {            string[] strArray = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,i,J,K,M,N,P,Q,R,S,T,U,W,X,Y,Z".Split(new char[] { ',' });            string str2 = "";            int num = -1;            Random random = new Random();            for (int i = 0; i < codeCount; i++)            {                if (num != -1)                {                    random = new Random((i * num) * ((int) DateTime.Now.Ticks));                }                int index = random.Next(0x23);                if (num == index)                {                    return this.CreateRandomCode(codeCount);                }                num = index;                str2 = str2 + strArray[index];            }            return str2;        }        private string GetRandomCode(int CodeCount)        {            string[] strArray = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,i,J,K,M,N,P,Q,R,S,T,U,W,X,Y,Z".Split(new char[] { ',' });            string str2 = "";            int num = -1;            Random random = new Random();            for (int i = 0; i < CodeCount; i++)            {                if (num != -1)                {                    random = new Random((num * i) * ((int) DateTime.Now.Ticks));                }                int index = random.Next(0x21);                while (num == index)                {                    index = random.Next(0x21);                }                num = index;                str2 = str2 + strArray[index];            }            return str2;        }        protected void Page_Load(object sender, EventArgs e)        {            string randomCode = this.GetRandomCode(4);            this.Session["CheckCode"] = randomCode;            this.SetPageNoCache();            this.CreateImage(randomCode);        }        private void SetPageNoCache()        {            base.Response.Buffer = true;            base.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1.0);            base.Response.Expires = 0;            base.Response.CacheControl = "no-cache";            base.Response.AppendHeader("Pragma", "No-Cache");        }   }

页面前面：

<script type="text/javascript">

function newGuid() {

var guid = "";

for (var i = 1; i <= 32; i++) {

var n = Math.floor(Math.random() * 16.0).toString(16);

guid += n;

if ((i == 8) || (i == 12) || (i == 16) || (i == 20))

guid += "-";

}

return guid;

}

function ChangeCode() {

var myImg = document.getElementById("ImageCheck");

myImg.src = "ValidateCode.aspx?flag=" + newGuid();

return false;

}

</script>

<input name="CheckCode" class="txtinput1" runat="server" type="text" id="CheckCode"/>

<img id="ImageCheck" οnclick="ChangeCode()" src="ValidateCode.aspx" alt="看不清楚，换一张" title="看不清楚，换一张" />

页面后面：

protected void btnSendMsg_Click(object sender, EventArgs e) {

if ((this.Session["CheckCode"] != null) && (this.Session["CheckCode"].ToString() != "")) {

if (this.Session["CheckCode"].ToString().ToLower() != this.CheckCode.Value.ToLower()) {

//this.lblMsg.Text = "验证码错误!";

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('验证码不正确!')", true);

this.Session["CheckCode"] = null;

return;

}

this.Session["CheckCode"] = null;

insertMsgToUs();

}

else {

base.Response.Redirect("Login.aspx");

}

}

 

例四：

verificationcode.aspx.cs：

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;using System.Drawing.Imaging;using System.Drawing.Drawing2D;using System.IO;public partial class verificationcode : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e) {        Response.Cache.SetCacheability(HttpCacheability.NoCache);        string vVerificationCode = RandomCode("verificationcode", 4, true);        Add("verificationcode", vVerificationCode.ToLower());   //Session中保存验证码        CreateImage(vVerificationCode);    }    /// 
    /// 从字符串里随机得到，规定个数的字符串.    /// 
    ///     ///     /// 是否要在生成前将当前线程阻止以避免重复    /// 
          public static string RandomCode(string byChar, int CodeCount, bool tSleep) {        string randomChar = "";        switch (byChar) {            case "num":                randomChar = "1,2,3,4,5,6,7,8,9";                break;            case "maxen":                randomChar = "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";                break;            case "minien":                randomChar = "a,b,c,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";                break;            case "minien&num":                randomChar = "1,2,3,4,5,6,7,8,9,a,b,c,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";                break;            case "all":                randomChar = "1,2,3,4,5,6,7,8,9,a,b,c,e,f,g,h,i,j,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,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";                break;            case "verificationcode":                randomChar = "2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";                break;            default:                randomChar = byChar;                break;        }        randomChar = randomChar.Replace(",", "");        string RandomCode = "";        if (tSleep) {            System.Threading.Thread.Sleep(3);        }        char[] allCharArray = randomChar.ToCharArray();        int n = allCharArray.Length;        System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));        for (int i = 0; i < CodeCount; i++) {            int rnd = random.Next(0, n);            RandomCode += allCharArray[rnd];        }        return RandomCode;    }    /// 
    /// 添加Session，有效期为20分钟    /// 
    /// Session对象名称    /// Session值数组    public static void Add(string strSessionName, string strValue) {        HttpContext.Current.Session[strSessionName] = strValue;        HttpContext.Current.Session.Timeout = 20;    }    #region 验证码        ///  
        ///  创建验证码图片        ///  
        ///  验证码        private void CreateImage(string randomcode)        {            int randAngle = 40; //随机转动角度            int mapwidth = (int)(randomcode.Length * 18);            Bitmap map = new Bitmap(mapwidth, 24);//创建图片背景            Graphics graph = Graphics.FromImage(map);            graph.Clear(Color.White);//清除画面，填充背景            //graph.DrawRectangle(new Pen(Color.Silver, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框            Random rand = new Random();            //验证码旋转，防止机器识别            char[] chars = randomcode.ToCharArray();//拆散字符串成单字符数组            //文字距中            StringFormat format = new StringFormat(StringFormatFlags.NoClip);            format.Alignment = StringAlignment.Center;            format.LineAlignment = StringAlignment.Center;            //定义颜色            Color[] c = { Color.Black, Color.Red, Color.Blue, Color.Green,                             Color.Orange, Color.Brown, Color.DarkBlue };            //画图片的背景噪音线            for (int i = 0; i < 2; i++)            {                int x1 = rand.Next(10);                int x2 = rand.Next(map.Width - 10, map.Width);                int y1 = rand.Next(map.Height);                int y2 = rand.Next(map.Height);                graph.DrawLine(new Pen(c[rand.Next(7)]), x1, y1, x2, y2);            }            for (int i = 0; i < chars.Length; i++)            {                int cindex = rand.Next(7);                int findex = rand.Next(5);                Font f = new System.Drawing.Font("Arial", 18, System.Drawing.FontStyle.Regular);//字体样式(参数2为字体大小)                Brush b = new System.Drawing.SolidBrush(c[cindex]);                Point dot = new Point(12, 16);                float angle = rand.Next(-randAngle, randAngle);//转动的度数                graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置                graph.RotateTransform(angle);                graph.DrawString(chars[i].ToString(), f, b, 1, 1, format);                graph.RotateTransform(-angle);//转回去                graph.TranslateTransform(2, -dot.Y);//移动光标到指定位置            }            //生成图片            System.IO.MemoryStream ms = new System.IO.MemoryStream();            map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            Response.ClearContent();            Response.ContentType = "image/gif";            Response.BinaryWrite(ms.ToArray());            graph.Dispose();            map.Dispose();        }        #endregion   }

页面前面

<input name="txtCode" runat="server" type="text" id="txtCode" class="txtinput1" />

<img src="verificationcode.aspx" οnclick="this.src='verificationcode.aspx?r=' + Math.random();" alt="点击刷新验证码" style="cursor: pointer;"/>

页面后面

protected void btnSendMsg_Click(object sender, EventArgs e) {

if ((this.Session["verificationcode"] != null) && (this.Session["verificationcode"].ToString() != "")) {

if (this.Session["verificationcode"].ToString() != this.txtCode.Value.ToLower()) {

ScriptManager.RegisterStartupScript(this, GetType(), "msg", "alert('验证码不正确!')", true);

this.Session["verificationcode"] = null;

return;

}

this.Session["verificationcode"] = null;

insertMsgToUs();

}

else {

base.Response.Redirect("Login.aspx");

}

}

 

 

再度应用的写法：

#region 生成随机的验证码        /// 
        /// 生成随机的验证码        /// 
        /// 
              private string GenerateCheckCode()        {            int number;            char code;            string checkCode = String.Empty;            System.Random random = new Random();            for (int i = 0; i < 5; i++)            {                number = random.Next();                if (number % 2 == 0)                    code = (char)('0' + (char)(number % 10));                else                    code = (char)('A' + (char)(number % 26));                checkCode += code.ToString();            }            //去掉0和大小写o            checkCode = checkCode.Replace("0", "1").Replace("o", "1").Replace("O", "1");            //if (!Request.Browser.Cookies)            //{            //    Session["validateCode"] = checkCode;            //}            //Response.Cookies.Add(new HttpCookie("validateCode", checkCode));            return checkCode;        }        /// 
        /// 生成随机的验证码        /// 
        /// 
              public string CreateCodeImage()        {            char[] chars = "23456789QWERTYUPASDFGHJKLZXCVBNMqwertyupasdfghjkzxcvbnm".ToCharArray();            Random random = new Random();            string validateCode = string.Empty;            for (int i = 0; i < 5; i++)                validateCode += chars[random.Next(0, chars.Length)].ToString();            return validateCode;        }        /// 
        /// 生成随机的验证码        /// 
        /// 
              public string CreateVerifyCode()        {            string codeSerial = "1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";            string[] arr = codeSerial.Split(',');            string code = "";            int randValue = -1;            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < 5; i++)            {                randValue = rand.Next(0, arr.Length - 1);                code += arr[randValue];            }            return code;        }        /// 
        /// 生成随机的验证码        /// 
        /// 
              private string CreateValidate()        {            string ValidateCode = string.Empty;            string AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";            //将验证码中所有的字符保存在一个字符串数组中            string[] CharArray = AllChar.Split(',');            int Temp = -1;            //生成一个随机对象            Random RandCode = new Random();            //根据验证码的位数循环            for (int i = 0; i < 5; i++)            {                //主要是防止生成相同的验证码                if (Temp != -1)                {                    //加入时间的刻度                    RandCode = new Random(i * Temp * ((int)DateTime.Now.Ticks));                }                int t = RandCode.Next(35);                if (Temp == t)                {                    //相等的话重新生成                    CreateValidate();                }                Temp = t;                ValidateCode += CharArray[Temp];            }            //错误检测,去除超过指定位数的验证码            if (ValidateCode.Length > 5)                ValidateCode = ValidateCode.Remove(5);            return ValidateCode;        }        #endregion

#region 将生成的验证码在网页上画出        /// 
        /// 将生成的验证码在网页上画出        /// 
        ///         private void CreateCheckCodeImage(string checkCode)        {            if (checkCode == null || checkCode.Trim() == String.Empty)                return;            Bitmap image = new Bitmap((int)Math.Ceiling(checkCode.Length * 12.5), 22);            Graphics g = Graphics.FromImage(image);            try            {                //生成随机生成器                Random random = new Random();                //清空图片背景色                g.Clear(Color.White);                //画图片的背景噪音线                for (int i = 0; i < 25; i++)                {                    int x1 = random.Next(image.Width);                    int x2 = random.Next(image.Width);                    int y1 = random.Next(image.Height);                    int y2 = random.Next(image.Height);                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);                }                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);                g.DrawString(checkCode, font, brush, 2, 2);                //画图片的前景噪音点                for (int i = 0; i < 100; i++)                {                    int x = random.Next(image.Width);                    int y = random.Next(image.Height);                    image.SetPixel(x, y, Color.FromArgb(random.Next()));                }                //画图片的边框线                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);                System.IO.MemoryStream ms = new System.IO.MemoryStream();                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);                Response.ClearContent();                Response.ContentType = "image/Gif";                Response.BinaryWrite(ms.ToArray());            }            finally            {                g.Dispose();                image.Dispose();            }        }        #endregion        /// 
        /// 将生成的验证码在网页上画出        /// 
        ///         private void CreateImage(string checkCode)        {            string[] fonts = { "Arial", "Georgia" };            Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };            ////文字距中            //StringFormat format = new StringFormat(StringFormatFlags.NoClip);            //format.Alignment = StringAlignment.Center;            //format.LineAlignment = StringAlignment.Center;            int letterWidth = 15;//单个字体的宽度范围            //int imageHeight = 27;//单个字体的高度范围            //int imageWidth = checkCode.Length * letterWidth + 5;            int fontSize = 12; int Padding = 2;            int randAngle = 40; //随机转动角度            int fWidth = fontSize + Padding;            int imageWidth = (int)(checkCode.Length * fWidth) + 4 + Padding * 2;            int imageHeight = fontSize * 2 + Padding;            Random newRandom = new Random();            Bitmap image = new Bitmap(imageWidth, imageHeight);            Graphics g = Graphics.FromImage(image);            //生成随机生成器            Random random = new Random();            //白色背景            g.Clear(Color.White);            //画图片的背景噪音线            for (int i = 0; i < 10; i++)            {                int x1 = random.Next(image.Width);                int x2 = random.Next(image.Width);                int y1 = random.Next(image.Height);                int y2 = random.Next(image.Height);                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);            }            //画图片的前景噪音点            for (int i = 0; i < 10; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));            }            //随机字体和颜色的验证码字符             int findex, cindex;            for (int int_index = 0; int_index < checkCode.Length; int_index++)            {                findex = newRandom.Next(fonts.Length - 1);                cindex = newRandom.Next(colors.Length - 1);                string str_char = checkCode.Substring(int_index, 1);                Brush newBrush = new SolidBrush(GetRandomColor());                //Brush newBrush = new SolidBrush(colors[cindex]);                Point thePos = new Point(int_index * letterWidth + 1 + newRandom.Next(3), 1 + newRandom.Next(3));//5+1+a+s+p+x                 //Point thePos = new Point(12, 16);                //float angle = newRandom.Next(-randAngle, randAngle);//转动的度数                 //g.TranslateTransform(thePos.X, thePos.Y);//移动光标到指定位置                //g.RotateTransform(angle);                 g.DrawString(str_char, new Font(fonts[findex], 14, FontStyle.Bold), newBrush, thePos);                //g.DrawString(checkCode[int_index].ToString(), new Font(fonts[findex], 14, FontStyle.Bold), newBrush, 1, 1, format);                //g.RotateTransform(-angle);//转回去                //g.TranslateTransform(2, -thePos.Y);//移动光标到指定位置            }            //灰色边框            //g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, imageWidth - 1, (imageHeight - 1));            g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1);            //图片扭曲            image = TwistImage(image, true, 3, 4);            //image = TwistImage(image, true, 8, 4);            //image = TwistImage(image, true, 0, 0);            //将生成的图片发回客户端            System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);            Response.ClearContent(); //需要输出图象信息 要修改HTTP头             Response.ContentType = "image/Png";            // Response.ContentType = "image/Gif";             // Response.ContentType = "image/Jpeg";            Response.BinaryWrite(ms.ToArray());            g.Dispose();            image.Dispose();        }        /// 
        /// 正弦曲线Wave扭曲图片        /// 
        /// 图片路径        /// 如果扭曲则选择为True        /// 波形的幅度倍数，越大扭曲的程度越高，一般为3        /// 波形的起始相位，取值区间[0-2*PI)        /// 
              private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)        {            const double PI2 = 3.1415926535897932384626433832795;            const double PI = 6.283185307179586476925286766559;            System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);            // 将位图背景填充为白色            System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);            graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);            graph.Dispose();            double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;            for (int i = 0; i < destBmp.Width; i++)            {                for (int j = 0; j < destBmp.Height; j++)                {                    double dx = 0;                    dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;                    dx += dPhase;                    double dy = Math.Sin(dx);                    // 取得当前点的颜色                    int nOldX = 0, nOldY = 0;                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);                    System.Drawing.Color color = srcBmp.GetPixel(i, j);                    if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)                    {                        destBmp.SetPixel(nOldX, nOldY, color);                    }                }            }            return destBmp;        }        /// 
        /// 生成随机颜色        /// 
        /// 
              private Color GetRandomColor()        {            Random RandomNum_First = new Random((int)DateTime.Now.Ticks);            System.Threading.Thread.Sleep(RandomNum_First.Next(50));            Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);            int int_Red = RandomNum_First.Next(210);            int int_Green = RandomNum_Sencond.Next(180);            int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;            int_Blue = (int_Blue > 255) ? 255 : int_Blue;            return Color.FromArgb(int_Red, int_Green, int_Blue);        }         #endregion

/// 
        /// 显示验证码图片        /// 
        public void CheckCodeImage()        {            string code = GenerateCheckCode();            //string code = CreateCodeImage();            //string code = CreateVerifyCode();            //string code = CreateValidate();            Session["checkImgCode"] = code;            //CreateCheckCodeImage(code);            CreateImage(code);        }

var flag = false;            if (Session["checkImgCode"] != null)            {                if (String.Compare(Session["checkImgCode"].ToString(), imgCode, true) != 0)                {                    res.msg = "图形验证码输入错误";                }                else                {                    flag = true;                }            }            else            {                res.msg = "图形验证码生成错误";            }

        $("#changeImgCode").click(function () {            var _this = $(this);            _this.attr("src", _this.attr("src") + "?v=" + Math.random());        });

 

gif验证码生成参考：http://blog.csdn.net/mowuyan/article/details/5431429