网页登陆校验码C#版代码

 [DefaultProperty("Text")]
     [ToolboxData("<{0}:ValidateCode runat=server></{0}:ValidateCode>")]
     public class ValidateCode : WebControl
     {
         /// <summary>
         /// 记录随机生成的验证码
         /// </summary>
         private string _checkCode = string.Empty;

         /// <summary>
         /// 用于记录验证码的位数，初始值为4
         /// </summary>
         private int _codeLen = ;

         /// <summary>
         /// Bindable：用于设置该属性是否可以绑定数据
         /// Category：设置属性显示在“按分类顺序”模式时，分组的类别名称
         /// Browsable：是否显示在控件的属性面板中
         /// DefaultValue：指定属性的默认值
         /// Description：指定属性的说明文字
         /// </summary>
         [Bindable(true), Category("Appearance"), Browsable(true), DefaultValue(true), Description("此属性用于设置验证码的长度")]
         public int CodeLength
         {
             get
             {
                 return _codeLen;
             }
             set
             {
                 _codeLen = value;
             }
         }

         /// <summary>
         /// 生成随机验证码
         /// </summary>
         /// <returns></returns>
         private string GetValidateCode()
         {
             //创建一个字符数组，用于存储组成验证码的数字和英文字母
             char[] s = new char[]{'','','','','','','','','a'
                 ,'b','c','d','e','f','g','h','i','j','k','m','n','p','q'
                 ,'r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G'
                 ,'H','I','J','K','L','M','N','P','Q','R','S','T','U','V','W'
                 ,'X','Y','Z'};
             string num = "";//创建变量用于记录指定长度的验证码的值
             Random r = new Random();//生成随机生成器
             //根据用户需要的长度来定义验证码的位数
             for (int i = ; i < _codeLen; i++)
             {
                 num += s[r.Next(, s.Length)].ToString();
             }
             return num;//返回生成的随机验证码的值
         }

         /// <summary>
         /// 绘制图形验证码
         /// </summary>
         /// <param name="checkCode">随机生成的验证码</param>
         private void CreateCheckCodeImage(string checkCode)
         {
             System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 14.5)), );//创建画布，用于绘制验证码
             Graphics g = Graphics.FromImage(image);//声明Graphics对象
             try
             {
                 Random random = new Random();            //生成随机生成器
                 g.Clear(Color.White);                        //清空图片背景色
                 Font font = new System.Drawing.Font("宋体", , (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));//设置字体
                 System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Green, Color.Red, 1.2f, true);//设置笔刷
                 g.DrawString(checkCode, font, brush, , );//将验证码绘制到画布中
                 for (int i = ; i < ; i++)            //画图片的前景噪音点
                 {
                     int x = random.Next(image.Width);
                     int y = random.Next(image.Height);
                     image.SetPixel(x, y, Color.FromArgb(random.Next()));
                 }
                 HttpContext.Current.Response.Cookies["code"].Value = checkCode;//将验证码存入cookie中
                 //画图片的边框线
                 g.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );
                 System.IO.MemoryStream ms = new System.IO.MemoryStream();//创建内存流
                 image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);//将验证码图片存入内存流
                 Page.Response.Clear();//清除缓冲区流中所有内容输出
                 Page.Response.ContentType = "image/GIF";//设置输出流类型
                 Page.Response.BinaryWrite(ms.ToArray());//写入输出流
                 Page.Response.Flush();//向客户端发送输出流
                 ms.Close();//释放资源
                 ms.Dispose();//释放资源
                 Page.Response.End();
             }
             catch (Exception ex)
             {
                 throw ex;
             }
             finally
             {
                 g.Dispose();
                 image.Dispose();
             }
         }

         /// <summary>
         /// 控件加载事件
         /// </summary>
         protected override void OnLoad(EventArgs e)
         {
             base.OnLoad(e);
             try
             {
                 string sn = Page.Request.QueryString["_ImageTag"];//获取页面传递的参数
                 if (sn != null)//判断参数是否为空，如果不为空时才能生成验证码，并绘制输出到页面
                 {
                     _checkCode = GetValidateCode();//生成验证码
                     CreateCheckCodeImage(_checkCode);//绘制输出到页面
                 }
                 else
                 {
                     //创建一个JavaScript函数用于生成随机数
                     string script = @"<script language='JavaScript'>
                                     function getnum()
                                     {
                                         var num=Math.floor(Math.random()*100);
                                         return num;
                                     }
                                     </script>";
                     //将该方法注册到控件所在的页面中
                     Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "getnum", script);
                 }
             }
             catch { }
         }

         protected override void RenderContents(HtmlTextWriter output)
         {
             string CID = string.Empty;
             try
             {
                 if (string.IsNullOrEmpty(_checkCode))//首先判断是否生成了验证码
                 {
                     CID = this.UniqueID + "img";//设置页面IMG的ID值
                     //输出表格到页面
                     output.Write("<table cellpadding=\"0\" cellspacing=\"0\" >");
                     output.Write("<tr>");
                     output.Write("<td>");
                     output.Write("<img border=\"0\" src=\"{0}\" id=\"{1}\"/>", this.Page.Request.Path + "?_ImageTag=" + DateTime.Now.Second, CID);//输出img图片，并且指定其src地址，因为验证码控件是被输出到当前的页面中，所以接收当前页面地址作为图片的数据源
                     output.Write("</td>");
                     output.Write("<td>");
                     output.Write("<a  style=\"cursor:pointer;font-size:small\" onclick=\"document.getElementById('" + CID + "').src=" + "'" + this.Page.Request.Path + "?_ImageTag='" + "+getnum()" + "\"" + ">&nbsp;&nbsp;看不清？</a>");//创建一个连接，单击后无刷新更换验证码
                     output.Write("</td>");
                     output.Write("</tr>");
                     output.Write("</table>");
                 }
             }
             catch
             {
                 output.Write("<table cellpadding=\"0\" cellspacing=\"0\" >");
                 output.Write("<tr>");
                 output.Write("<td>");
                 output.Write("</td>");
                 output.Write("<td>");
                 //显示“看不清？”链接
                 output.Write("<a  style=\"cursor:pointer;font-size:small\"" + ">&nbsp;&nbsp;看不清？</a>");
                 output.Write("</td>");
                 output.Write("</tr>");
                 output.Write("</table>");
             }
         }

         /// <summary>
         /// 公共方法用于验证输入的验证码是否正确
         /// </summary>
         public bool CheckSN(string sn)
         {
             bool flag = false;
             if (HttpContext.Current.Request.Cookies["code"].Value != null)//如果cookie不为空
             {
                 flag = sn.ToLower() == HttpContext.Current.Request.Cookies["code"].Value.ToString().ToLower();//判断记录的cookie与输入的验证码是否一致
             }
             return flag;
         }

     }