ASP.NET 生成验证码

新建一个ashx文件

  
    

   
     
   
     using
   
      System;

   
     using
   
      System.Drawing;

   
     using
   
      System.Drawing.Imaging;

   
     using
   
      System.Text;

   
     using
   
      System.Web;

   
     using
   
      System.Web.SessionState;


   
     namespace
   
      ValidateCode
{
 
   
     ///
   
      
   
     <summary>
   
     
 
   
     ///
   
      Summary description for $codebehindclassname$
 
   
     ///
   
      
   
     </summary>
   
     

   
     
 
   
     public
   
      
   
     class
   
      ImageCode : IHttpHandler,IRequiresSessionState
 {

 
   
     public
   
      
   
     void
   
      ProcessRequest(HttpContext context)
 {
 context.Response.ContentType 
   
     =
   
      
   
     "
   
     image/gif
   
     "
   
     ;
 
   
     //
   
     建立Bitmap对象，绘图
   
     

   
      Bitmap basemap 
   
     =
   
      
   
     new
   
      Bitmap(
   
     200
   
     , 
   
     60
   
     );
 Graphics graph 
   
     =
   
      Graphics.FromImage(basemap);
 graph.FillRectangle(
   
     new
   
      SolidBrush(Color.White), 
   
     0
   
     , 
   
     0
   
     , 
   
     200
   
     , 
   
     60
   
     );
 Font font 
   
     =
   
      
   
     new
   
      Font(FontFamily.GenericSerif, 
   
     48
   
     , FontStyle.Bold, GraphicsUnit.Pixel);
 Random r 
   
     =
   
      
   
     new
   
      Random();
 
   
     string
   
      letters 
   
     =
   
      
   
     "
   
     ABCDEFGHIJKLMNPQRSTUVWXYZ
   
     "
   
     ;
 
   
     string
   
      letter;
 StringBuilder s 
   
     =
   
      
   
     new
   
      StringBuilder();

 
   
     //
   
     添加随机的五个字母
   
     

   
      
   
     for
   
      (
   
     int
   
      x 
   
     =
   
      
   
     0
   
     ; x 
   
     <
   
      
   
     5
   
     ; x
   
     ++
   
     )
 {
 letter 
   
     =
   
      letters.Substring(r.Next(
   
     0
   
     , letters.Length 
   
     -
   
      
   
     1
   
     ), 
   
     1
   
     );
 s.Append(letter);
 graph.DrawString(letter, font, 
   
     new
   
      SolidBrush(Color.Black), x 
   
     *
   
      
   
     38
   
     , r.Next(
   
     0
   
     , 
   
     15
   
     ));
 }

 
   
     //
   
     混淆背景
   
     

   
      Pen linePen 
   
     =
   
      
   
     new
   
      Pen(
   
     new
   
      SolidBrush(Color.Black), 
   
     2
   
     );
 
   
     for
   
      (
   
     int
   
      x 
   
     =
   
      
   
     0
   
     ; x 
   
     <
   
      
   
     6
   
     ; x
   
     ++
   
     )
 graph.DrawLine(linePen, 
   
     new
   
      Point(r.Next(
   
     0
   
     , 
   
     199
   
     ), r.Next(
   
     0
   
     , 
   
     59
   
     )), 
   
     new
   
      Point(r.Next(
   
     0
   
     , 
   
     199
   
     ), r.Next(
   
     0
   
     , 
   
     59
   
     )));

 
   
     //
   
     将图片保存到输出流中 
   
     

   
      basemap.Save(context.Response.OutputStream, ImageFormat.Gif);
 context.Session[
   
     "
   
     CheckCode
   
     "
   
     ] 
   
     =
   
      s.ToString(); 
   
     //
   
     如果没有实现IRequiresSessionState，则这里会出错，也无法生成图片
   
     

   
      context.Response.End();
 }

 
   
     public
   
      
   
     bool
   
      IsReusable
 {
 
   
     get
   
      { 
   
     return
   
      
   
     true
   
     ; }
 }
 }
}


  
    

使用方法：在aspx页面上

 

  
    

   
     
   
     <
   
     asp:TextBox 
   
     ID
   
     ="txtValidate"
   
      runat
   
     ="server"
   
     ></
   
     asp:TextBox
   
     >
   
     

   
     <
   
     img 
   
     src
   
     ="ImageCode.ashx"
   
      alt
   
     ="图片验证码"
   
      
   
     />
   
     

   
     <
   
     asp:LinkButton 
   
     ID
   
     ="LinkButton1"
   
      runat
   
     ="server"
   
      OnClick
   
     ="LinkButton1_Click"
   
     >
   
     换一张
   
     </
   
     asp:LinkButton
   
     >
  
    

.cs中

 

  
    

   
     
   
     protected
   
      
   
     void
   
      btnValidate_Click(
   
     object
   
      sender, EventArgs e)
 {
 
   
     string
   
      imageCode 
   
     =
   
      Session[
   
     "
   
     CheckCode
   
     "
   
     ].ToString();
 
   
     string
   
      script 
   
     =
   
      
   
     string
   
     .Empty;
 
   
     if
   
      (
   
     this
   
     .txtValidate.Text.Trim().ToUpper() 
   
     ==
   
      imageCode)
 {
 script 
   
     =
   
      
   
     "
   
     alert('successful');
   
     "
   
     ;

 }
 
   
     else
   
     
 {
 script 
   
     =
   
      
   
     "
   
     alert('fail');
   
     "
   
     ;
 }
 
   
     this
   
     .Page.ClientScript.RegisterStartupScript(
   
     this
   
     .Page.GetType(), 
   
     "
   
     alert
   
     "
   
     , script, 
   
     true
   
     );
 }