AJAX基础知识

ASP页面
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>AJAX之加法运算示例</title>
    <script type="text/javascript">
        var xmlHttp;
        function createXMLHttpRequest()
        {
            if(window.ActiveXObject)
            {
                xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            else if(window.XMLHttpRequest)
            {
                xmlHttp = new XMLHttpRequest();
            }
        }
        function addNumber()
        {
            createXMLHttpRequest();
            var url= "Handler.ashx?Num1="+document.getElementById("num1").value+"&Num2="+document.getElementById("num2").value;
            xmlHttp.open("GET",url,true);
            xmlHttp.onreadystatechange=showResult;
            xmlHttp.send(null);
        }
        function showResult()
        {
            if(xmlHttp.readyState==4)
            {
                if(xmlHttp.status==200)
                {
                    document.getElementById("result").value=xmlHttp.responseText;
                }
            }
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div style="text-align: center">
        <input id="num1" style=" 99px" type="text" value="0" onkeyup="addNumber();" />+<input id="num2" style=" 95px"
            type="text" value="0" onkeyup="addNumber();" />=<input id="result" style=" 99px" type="text" /></div>
    </form>
</body>
</html>

Handler.ashx文件
<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;

public class Handler : IHttpHandler {

    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        int result = Convert.ToInt32(context.Request.QueryString["Num1"]) + Convert.ToInt32(context.Request.QueryString["Num2"]);
        context.Response.Write(result);
    }

    public bool IsReusable {
        get {
            return false;
        }
    }

}