字母与数字混合的验证码

字母和数字混合验证码技术是网站注册和登录模块中经常用到的验证技术，开发人员可以通过验证码技术来阻止用户的非法操作。由于验证码存放在客户端机器的Cookie中，在调用时，可直接将文本框中的数据和Cookie中的数据进行对照。从客户端机器中的Cookie中取值。

  
    

   
      
   
     protected
   
      
   
     void
   
      Page_Load(
   
     object
   
      sender, EventArgs e)
 {
 CreateCheckCodeImage(GenerateCheckCode());
 }
  
    

  
    

   
      
   
     private
   
      
   
     void
   
      CreateCheckCodeImage(
   
     string
   
      checkCode)
 {
 
   
     if
   
      (checkCode 
   
     ==
   
      
   
     null
   
      
   
     ||
   
      checkCode.Trim() 
   
     ==
   
      String.Empty)
 
   
     return
   
     ;

 System.Drawing.Bitmap image 
   
     =
   
      
   
     new
   
      System.Drawing.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 
   
     <
   
      
   
     2
   
     ; 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.Black), 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
   
     

   
      
   
     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();
 }
 }
  
    

  
    

   
      
   
     private
   
      
   
     string
   
      GenerateCheckCode()
 {
 
   
     int
   
      number;
 
   
     char
   
      code;
 
   
     string
   
      checkCode 
   
     =
   
      String.Empty;

 Random random 
   
     =
   
      
   
     new
   
      Random();

 
   
     for
   
      (
   
     int
   
      i 
   
     =
   
      
   
     0
   
     ; i 
   
     <
   
      
   
     4
   
     ; i
   
     ++
   
     )
 {
 number 
   
     =
   
      random.Next();

 
   
     if
   
      (number 
   
     %
   
      
   
     2
   
      
   
     ==
   
      
   
     0
   
     )
 code 
   
     =
   
      (
   
     char
   
     )(
   
     '
   
     0
   
     '
   
      
   
     +
   
      (
   
     char
   
     )(number 
   
     %
   
      
   
     10
   
     ));
 
   
     else
   
     
 code 
   
     =
   
      (
   
     char
   
     )(
   
     '
   
     A
   
     '
   
      
   
     +
   
      (
   
     char
   
     )(number 
   
     %
   
      
   
     26
   
     ));

 checkCode 
   
     +=
   
      code.ToString();
 }

 Response.Cookies.Add(
   
     new
   
      HttpCookie(
   
     "
   
     CheckCode
   
     "
   
     , checkCode));

 
   
     return
   
      checkCode;
 }