ASP.net中的验证码实现全过程

1.新建一个页面A.aspx，作为制作验证码的实现页   代码如下

     Protected    ovid  Page_Load(object sender,EventArgs e )

          {

              string  path=Server.MapPath（"../image/code.jpg"）;

              System.Drawing.Image   image=System.Drawing.Image.FromFile( path );

                  //在图片场景中创建绘图对象Graphics

              Graphics   g=Graphics.FromImage( image );

              Font   font =new   Font( "宋体"  , 20 , FontStyle.Italic ) ;

              SolidBrush  brush =new SolidBrush( Color.Blue );

              PointF    pf = new  PointF( 2f , 2f );

             string     str=GetString( 4 );

             //将随即生成的验证码保存在Session中，方便在需要验证码的页面来验证

             Session["SN"] = str ;

             g.DrawString( str , font , brush , pf );

                //通常我们利用Response的响应流来达到不同的数据请求目的

             image.Save( ReSpone.OutputStream , System.Drawing.Imaging.ImageFormat.JPG ) ;

             g.Dispose();

             image.Dispose();

             ReSponse.End();

         }

                  //下面方法为随机生成验证码

     Protected   void   GetString( int   num ) 

           {

                  string   str="";

                   string[]   strarray={ "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "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" }; 

                  Random    r= new  Random();

                 for( int i=0 ; i<num ; i++)

                        {

                              str+= strarray[ r.Next( strarray.Length ) ] ;

                         }

                  return   str;

           } 

 

2. 在验证页面中  加一个Image 控件 和一个Html  按钮 控件( 设置其为LinkButton样式 )

          a.实现显示验证码 ：

                     在Image  控件属性中 设置其  ImageUrl = "A.aspx" ; //(也就是上面的实现验证码页)

         b.实现HTMl 按钮局部刷新 验证码

                   。 设置HTMl  按钮样式   其VALue=“看不清换一张"

                   。在前台页面代码</head>前加如下代码

                                   <script  type="txtt/javascript">

                                         function   Look()

                                           {

                                                document.GetElementById("Image1").src=' A.aspx?' +Math.random() ;

                                           }

                                   </script>

                    。在HTml  按钮中加如下 黄色部份代码

                              <input  id=" Button1"  onclick="Look()" ……>