验证码

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，记的要导入System

 {        

public void ProcessRequest (HttpContext context)    

     {         string cheakCode=GenCode(5);//产生5位随机字符   

      context.Session["Code"]=cheakCode;//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;    

      }   

}