.NET中实现无客户端联动菜单 (无刷新)

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false" Inherits="CustomManager.company.WebForm1" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
    <title>WebForm1</title>
    <meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
    <meta content="C#" name="CODE_LANGUAGE">
    <meta content="JavaScript" name="vs_defaultClientScript">
    <meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
    <LINK href="../css/style.css" type="text/css" rel="stylesheet">
</HEAD>
<body MS_POSITIONING="GridLayout">
    <form id="Form1" method="post" runat="server">
     <asp:dropdownlist id="DropDownList1" style="Z-INDEX: 101; LEFT: 40px; POSITION: absolute; TOP: 168px"
    runat="server"></asp:dropdownlist><asp:label id="Label1" style="Z-INDEX: 102; LEFT: 328px; POSITION: absolute; TOP: 104px" runat="server">Label</asp:label>
     <asp:DropDownList id="DropDownList2" style="Z-INDEX: 104; LEFT: 40px; POSITION: absolute; TOP: 264px"
    runat="server"></asp:DropDownList></form>
<script LANGUAGE="javascript">
var str = document.getElementById("Label1").innerText;
arr=str.split(",");
a=arr.length
ar=new Array()
for (i=0;i<a;i++){
ar[i]=arr[i].split("-");
}
onecount=ar.length;
function ld() {
document.Form1.DropDownList2.length=0
lid=Form1.DropDownList1.value;
for (i=0;i<onecount;i++) {

补充：asp教程,高级应用