AJAX基本应用

// AJAX基本应用:
// 两个数相加:用到一个基本应用程序页面!!
<% @ Page Language = " C# "  AutoEventWireup = " true "   CodeFile = " Default.aspx.cs "  Inherits = " _Default "   %>
< html xmlns = " http://www.w3.org/1999/xhtml "   >
< head runat = " server " >
     < title > 无标题页 </ title >
     < script type = " text/javascript " >
        var xmlHttpRequest;
        function createXMLHttpRequest()
         ... {
            if(window.ActiveXObject)
            ...{
                xmlHttpRequest=new ActiveXObject("Microsoft.XMLHTTP");
            }
            else if(window.XMLHttpRequest)
            ...{
                xmlHttpRequest=new XMLHttpRequest();
            }
        }
        function addNumber()    // startRequest()
         ... {
            createXMLHttpRequest();
            var url="Handler.ashx?Num1="+document.getElementById("num1").value+"&Num2="+document.getElementById("num2").value;
            xmlHttpRequest.open("get",url,true);
            xmlHttpRequest.onreadystatechange=showResult;
            xmlHttpRequest.send(null);
        }
        function showResult()
         ... {
            if(xmlHttpRequest.readyState==4)
            ...{
                if(xmlHttpRequest.status==200)
                ...{
                    document.getElementById("result").value=xmlHttpRequest.responseText;
                }
            }
        }
     </ script >
</ head >
< body >
     < form id = " form1 "  runat = " server " >
     < div style = " text-align: center " >
         < asp:TextBox ID = " num1 "  runat = " server "  onkeyup = " addNumber(); " ></ asp:TextBox >+
         < asp:TextBox ID = " num2 "  runat = " server "  onkeyup = " addNumber(); " ></ asp:TextBox >
         =< asp:TextBox ID = " result "  runat = " server " ></ asp:TextBox >< br  />
    
     </ div >
     </ form >
</ body >
</ html >

// 基本应用程序页面
<% @ WebHandler Language = " C# "  Class = " Handler "   %>

using  System;
using  System.Web;

public   class  Handler : IHttpHandler  ... {
    
    public void ProcessRequest (HttpContext context) ...{
        context.Response.ContentType = "text/plain";
        try
        ...{
            int result = Convert.ToInt32(context.Request.QueryString["Num1"]) + Convert.ToInt32(context.Request.QueryString["Num2"]);
            context.Response.Write(result);
        }
        catch(FormatException e )
        ...{
            context.Response.Write("请输入另一个数字!");
        }
       
    }
 
    public bool IsReusable ...{
        get ...{
            return false;
        }
    }

}