.NET使用一般处理程序生成验证码

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 <html> 
 <head> 
 <title></title> 
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 
 </head> 
 <body> 
 <img src="WaterMark.ashx" id="vimg" alt="" onclick="document.getElementById('vimg').src='this.src+='+?;" title="看不清楚，点击换一张" />
 </body> 
 </html>

using System;   
 using System.Web;   
 using System.Drawing;   
 using System.Drawing.Drawing2D;   
 using System.Web.SessionState;     
   
 public class WaterMark : IHttpHandler, IRequiresSessionState  //  要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间   
 {   
   
     public void ProcessRequest(HttpContext context)   
     {   
         string checkCode = GenCode(5);  // 产生5位随机字符   
         context.Session["Code"] = checkCode; //将字符串保存到Session中，以便需要时进行验证   
         System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 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   
             int i;   
             for (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 System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));   
             System.Drawing.Drawing2D.LinearGradientBrush brush =  new System.Drawing.Drawing2D.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   
             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);   
             context.Response.ClearContent();   
             context.Response.ContentType = "image/Gif";   
             context.Response.BinaryWrite(ms.ToArray());   
         }   
         finally  
         {   
             g.Dispose();   
             image.Dispose();   
         }   
     }   
   
     /// <summary>   
 /// 产生随机字符串   
 /// </summary>   
 /// <param name="num">随机出几个字符</param>   
 /// <returns>随机出的字符串</returns>
     private string GenCode(int num)   
     {   
         string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
         char[] chastr = str.ToCharArray();   
         // string[] source ={ "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", "#", "$", "%", "&", "@" };   
         string code = "";   
         Random rd = new Random();   
         int i;   
         for (i = 0; i < num; i++)   
         {   
             //code += source[rd.Next(0, source.Length)];   
             code += str.Substring(rd.Next(0, str.Length), 1);   
         }   
         return code;   
   
     }   
   
     public bool IsReusable   
     {   
         get  
         {   
             return false;   
         }   
     }   
   
 }

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