为什么我的updatepanel不起作用？

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %><%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
    Namespace="System.Web.UI" TagPrefix="asp" %><!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>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="ScriptManager2" runat="server"> 
        </asp:ScriptManager> 
        <asp:UpdatePanel ID="UpdatePanel3" runat="server"> 
        <ContentTemplate> 
            <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" Width="205px" 
            OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged"> 
                <asp:ListItem>1</asp:ListItem>
                <asp:ListItem>2</asp:ListItem>
            </asp:DropDownList> 
        </ContentTemplate> 
        </asp:UpdatePanel>
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label></div>
    </form>
</body>
</html>
——————————————————————
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.Label1.Text = DateTime.Now.ToString();
    }
    
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        
    }
}
———————————————————————— 

解决方案 »

  1.   

    加上
    <httpHandlers>
    　<remove verb="*" path="*.asmx"/>
    　<add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35"/>
    　<add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35"/>
    　<add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler,System.Web.Extensions,Version=1.0.61025.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35" validate="false"/>
    </httpHandlers >
      

  2.   

    web.config要怎么设置？我才接触这个东西 不懂……
      

  3.   

    虽然是不刷新了 但是为什么还是会执行page_load?
      

  4.   

    protected void Page_Load(object sender, EventArgs e)
    {
        if(!Page.IsPostBack)
        {
            this.Label1.Text = DateTime.Now.ToString();
        }
    }