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bobojavascript、asp.net 实现随机生成验证码

一些网站中都有登录页面,登录时输入正确的验证码才可以,废话不多说,今天就用javascript

        和异步来实现自动生成图片验证码的功能。

        首先我们要插入一个一般处理程序(也就是ashx的文件,这里我给它起名为WaterMark.ashx)

        这个文件所包括的引用:

        using System;
        using System.Web;
        using System.Drawing;
        using System.Drawing.Drawing2D;
        using System.Web.SessionState; //在ashx文件中要使用Session就要添加此引用

        具体代码如下:

        public class WaterMark : IHttpHandler, IRequiresSessionState  // 要使用session必须实现该接口
      {
          public void ProcessRequest(HttpContext context)
          {
              string checkCode = GenCode(4);  // 产生4位随机字符
              context.Session["Code"] = checkCode; //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(58, 22);//图片大小
              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";//图片上随机文字
              char[] chastr = str.ToCharArray();
              string code = "";
              Random rd = new Random();
              int i;
              for (i = 0; i < num; i++)
              {
                  code += str.Substring(rd.Next(0, str.Length), 1);
              }
              return code;
          }
          public bool IsReusable
          {
              get
              {
                  return false;
              }
          }
      }

      一般处理程序写完后,接着我们整理前台页面,为了能点击此图片能切换图片上的文字

         我们在hand里写上如下javascript切换事件

           <script language="javascript" type="text/javascript">
        function changeCode() {   
           var imgNode = document.getElementById("vimg");   

              // 这里加个时间的参数是为了防止浏览器缓存的问题
           imgNode.src = "http://www.mamicode.com/WaterMark.ashx?t=" + (new Date()).valueOf();    
        }  
       </script>

    接着在想要显示这个随机验证图片的地方加入:

           验证码:<img src="http://www.mamicode.com/WaterMark.ashx" id="vimg" onclick="changeCode()"/>
           <asp:TextBox ID="txtCode" runat="server"></asp:TextBox>

           最后我们只需要在.cs页面上判断txtCode的值和Session["Code"]的值是否想等就可以了

           if(txtCode.Text.Trim()==Session["Code"])

     {

               Response.Write("验证码输入正确!");

     }

            else

            {

               Response.Write("验证码输入错误!请重新输入");

            }