无刷新验证码

放验证码的页面内添加如下js脚本，这个是刷新验证码的方法：

[html]
<script language="javascript" type="text/javascript">
function fresh()
{
var randomnum=Math.random();
var getimagecode=document.getElementById( "codeimage");
getimagecode.src= "ValidateImage.aspx? "+randomnum;
}
</script>

页面内要放验证码的地方（层内，单元格内等）放置如下代码，这个是验证码的图图，输入验证码的文本框和调刷新方法的链接。

[html]
<div><img id="codeimage" src="ValidateImage.aspx?,Math.random()" />
<asp:TextBox ID="txtValidateCode" runat="server" Width="55px" MaxLength="4"></asp:TextBox>
<a href="javascript:fresh()" style="font-size: 12px; color: Green">看不清</a></div>

Validateimage.aspx页面是生成图片

[html] view plaincopyprint?private void Page_Load(object sender, System.EventArgs e)
   {
       this.CreateCheckCodeImage(RndNum());
   }
   private string RndNum()
   {
       int number;
       char code;
       string checkCode = String.Empty;

       System.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("yzmcode", checkCode));
       return checkCode;
   }
   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 < 20; 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.Aqua), x1, y1, x2, y2);
           }

           Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
           System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.BlueViolet, Color.BlueViolet, 1.2f, true);
           g.DrawString(checkCode, font, brush, 2, 2);
           //画图片的前景噪音点
           for (int i = 0; i < 50; 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();
       &nb

补充：web前端 , HTML/CSS  ,