如何使用ASP.NET实现生成验证码功能的实例代码

本文实例讲述了ASP.NET实现的生成验证码功能。分享给大家供大家参考，具体如下：

生成验证码原理：产生随机字符，并将字符生成为图片，同时储存到Session里去，然后验证用户输入的内容是否与Session中的验证码相符即可。

效果图：用户可以点击切换验证码信息。

一般处理程序：CheckCodeHandler.cs

<%@ WebHandler Language="C#" Class="CheckCodeHandler" %>  using System;  using System.Web;  using System.Text;  using System.Drawing;  using System.Web.SessionState;  public class CheckCodeHandler : IHttpHandler,IRequiresSessionState  {    //产生验证码的字符集    public string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";    public void ProcessRequest (HttpContext context) {      string validateCode = CreateRandomCode(4);      context.Session["ValidateCode"] = validateCode;//将验证码保存到session中      CreateCodeImage(validateCode, context);    }    public bool IsReusable {      get {        return false;      }    }    /// <summary>    /// 生成验证码    /// </summary>    /// <param name="n">验证码个数</param>    /// <returns>验证码字符串</returns>    public string CreateRandomCode(int n)    {      string[] CharArray = charcode.Split(',');//将字符串转换为字符数组      string randomCode = "";      int temp = -1;      Random rand = new Random();      for (int i = 0; i < n; i++)      {        if (temp != -1)        {          rand = new Random(i * temp * ((int)DateTime.Now.Ticks));        }        int t = rand.Next(CharArray.Length - 1);        if (temp != -1 && temp == t)        {          return CreateRandomCode(n);        }        temp = t;        randomCode += CharArray[t];      }      return randomCode;    }    public void CreateCodeImage(string checkCode, HttpContext context)    {      int iwidth = (int)(checkCode.Length * 13);      System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);      Graphics g = Graphics.FromImage(image);      Font f = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Italic | System.Drawing.FontStyle.Bold));      // 前景色      Brush b = new System.Drawing.SolidBrush(Color.Black);      // 背景色      g.Clear(Color.White);      // 填充文字      g.DrawString(checkCode, f, b, 0, 1);      // 随机线条      Pen linePen = new Pen(Color.Gray, 0);      Random rand = new Random();      for (int i = 0; i < 5; i++)      {        int x1 = rand.Next(image.Width);        int y1 = rand.Next(image.Height);        int x2 = rand.Next(image.Width);        int y2 = rand.Next(image.Height);        g.DrawLine(linePen, x1, y1, x2, y2);      }      // 随机点      for (int i = 0; i < 30; i++)      {        int x = rand.Next(image.Width);        int y = rand.Next(image.Height);        image.SetPixel(x, y, Color.Gray);      }      // 边框      g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);      // 输出图片      System.IO.MemoryStream ms = new System.IO.MemoryStream();      image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);      context.Response.ClearContent();      context.Response.ContentType = "image/jpeg";      context.Response.BinaryWrite(ms.ToArray());      g.Dispose();      image.Dispose();    }  }

封装成类库：ValidateNumber.cs

using System;  using System.Collections.Generic;  using System.Linq;  using System.Web;  using System.Drawing;  using System.Web.UI;  using System.Drawing.Drawing2D;  using System.IO;  using System.Drawing.Imaging;  /// <summary>  ///ValidateNumber 生成验证码  /// </summary>  public class ValidateNumber  {    //产生验证码的字符集 （易混淆的字符去掉）    private string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";    /// <summary>    /// 验证码的最大长度    /// </summary>    public int MaxLength    {      get { return 10; }    }    /// <summary>    /// 验证码的最小长度    /// </summary>    public int MinLength    {      get { return 1; }    }    /// <summary>    /// 生成验证码    /// </summary>    /// <param name="length">指定验证码的长度</param>    /// <returns></returns>    public string CreateValidateNumber(int length)    {      string[] CharArray = charcode.Split(',');//将字符串转换为字符数组      string randomCode = "";      int temp = -1;      Random rand = new Random();      for (int i = 0; i < length; i++)      {        if (temp != -1)        {          rand = new Random(i * temp * ((int)DateTime.Now.Ticks));        }        int t = rand.Next(CharArray.Length - 1);        if (temp != -1 && temp == t)        {          return CreateValidateNumber(length);        }        temp = t;        randomCode += CharArray[t];      }      return randomCode;    }    /// <summary>    /// 创建验证码的图片    /// </summary>    /// <param name="context">context对象</param>    /// <param name="validateNum">验证码</param>    public void CreateValidateGraphic(HttpContext context,string validateNum)    {      int iwidth = (int)(validateNum.Length * 14);      Bitmap image = new Bitmap(iwidth, 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);        //画图片的干扰线        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(validateNum, font, brush, 3, 2);        //画图片的前景干扰点        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);        //保存图片数据        MemoryStream stream = new MemoryStream();        image.Save(stream, ImageFormat.Jpeg);        //输出图片        context.Response.Clear();        context.Response.ContentType = "image/jpeg";        context.Response.BinaryWrite(stream.ToArray());      }      finally      {        g.Dispose();        image.Dispose();      }    }    /// <summary>    /// 得到验证码图片的长度    /// </summary>    /// <param name="validateNumLength">验证码的长度</param>    /// <returns></returns>    public static int GetImageWidth(int validateNumLength)    {      return (int)(validateNumLength * 14);    }    /// <summary>    /// 得到验证码图片的高度    /// </summary>    /// <returns></returns>    public static double GetImageHeight()    {      return 22;    }  }

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