牛腩新闻发布系统——初探Javascript

         JavaScript是一种基于对象和事件驱动并具有相对安全性的客户端脚本语言。同时也是一种广泛用于客户端Web开发的脚本语言，常用来给HTML网页添加动态功能，比如响应用户的各种操作。在牛腩新闻发布系统中有一下应用。

一、错误界面中的倒计时。

aspx文件的Javascript代码：

 <script language ="javascript" type ="text/javascript" >
        var i = 5;
        var intervalid;
        intervalid = setInterval("fun()", 1000);
        function fun() {
            if (i == 0) {
                window.location.href = "Default.aspx";
                clearInterval(intervalid);
            }
            document.getElementById("mes").innerHTML = i;
            i--;
        }
</script>
  <p>将在<span id="mes">5</span>秒钟返回界面</p>





 
二、验证码。
先建立一个一般处理程序。代码如下：
<%@ WebHandler Language="C#" Class="WaterMark" %>


using System;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Web.SessionState;  

public class WaterMark : IHttpHandler, IRequiresSessionState  // 要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间
{

    public void ProcessRequest(HttpContext context)
    {
        string checkCode = GenCode(5);  // 产生5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(70, 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
            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";
        char[] chastr = str.ToCharArray();
        // string[] source ={ "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", "#", "$", "%", "&", "@" };
        string code = "";
        Random rd = new Random();
        int i;
        for (i = 0; i < num; i++)
        {
            //code += source[rd.Next(0, source.Length)];
            code += str.Substring(rd.Next(0, str.Length), 1);
        }
        return code;

    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}

Aspx的代码：
开头有一段Javascript的代码：
<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
<script language ="javascript" type ="text/javascript">
        function changeCode() {
        var imgNode = document.getElementById("vimg");
        imgNode.src = "WaterMark.ashx?t=" + (new Date()).valueOf(); // 这里加个时间的参数为了防止浏览器缓存的问题  
    }  
</script>
  <p>
        验证码：<a name="com"> </a><img src="WaterMark.ashx" id="vimg" alt="" onclick ="changeCode()" />
        <asp:TextBox ID="txtCode" ValidationGroup ="pinglun"  runat="server" CssClass ="txtCode"></asp:TextBox>
          <asp:RequiredFieldValidator ValidationGroup ="pinglun"  ID="RequiredFieldValidator1" runat="server"  ControlToValidate ="txtCode" ErrorMessage="请输入验证码"  Text ="*"></asp:RequiredFieldValidator>
        <asp:Button ID="BtnSub" ValidationGroup ="pinglun" runat="server" Text="提交" onclick="BtnSub_Click" />
        <asp:ValidationSummary ValidationGroup ="pinglun" ID="ValidationSummary1" runat="server" ShowMessageBox="true" ShowSummary ="false"   />
        </p>