asp.net中的验证码

要实现如图的效果的验证码，分以下步骤：

第一、布局好调用验证码的登录页面（命名：Login.aspx），注意：验证码位置可以是服务器控件 Image，也可以是html标签写的<img>，但是图片url就是一个页面（命名：ValidateCode.aspx）(将在下面讲述。)比如：<asp:Image ID=“vcImg”      ImageUrl="~/ValidateCode.aspx"   runat="server" />

第二、生成类文件 (命名：validatedCode）

using System;using System.Data;using System.Configuration;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;using System.Drawing;using System.IO;using System.Drawing.Imaging;/// <summary>/// Summary description for validatedCode/// </summary>public class validatedCode{          #region  验证码长度(默认6个验证码的长度)        int length = 4;        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 = 40;        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 = "0,1,2,3,4,5,6,7,8,9,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,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";        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;        /// <summary>        /// 正弦曲线Wave扭曲图片（Edit By 51aspx.com）        /// </summary>        /// <param name="srcBmp">图片路径</param>        /// <param name="bXDir">如果扭曲则选择为True</param>        /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>        /// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>        /// <returns></returns>        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（Add By 51aspx.com）            image = TwistImage(image, true, 8, 4);            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}

PS：虽然不是我自己写的，但是可分享给大家。

代码中有注释，所以我就不多说了。

第三、生成调用类文件的网页（ValidateCode.aspx），在该页面的后台代码（ValidateCode.aspx.cs文件）的Page_Load事件中写如下代码：

    protected void Page_Load(object sender, EventArgs e)    {        validatedCode v = new validatedCode();        string code = v.CreateVerifyCode();            //取随机码        v.CreateImageOnPage(code, this.Context);       // 输出图片        Session["CheckCode"] = code;                   //Session 取出验证码    }

第四、判断验证结果：Login.aspx页面的登录事件中添加验证

 protected void btnLogin_Click(object sender, EventArgs e)    {        string vCode = Session["CheckCode"].ToString();        if (txtValidatedcode.Text.Trim().ToUpper() == vCode.ToUpper())        {            ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Startup", "alert('ValidatedCode is right!');", true);        }    }