asp.net如何利用两个listbox控件做联动？

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    首先，新建一个web窗体，然后在工具栏拖拽两个listbox控件到页面上，如下面的示例：

<% ... @ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false" Inherits="WebApp.WebForm1"  %>
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"  >
< HTML >
     < HEAD >
         < title > WebForm1 </ title >
         < meta  name ="GENERATOR"  Content ="Microsoft Visual Studio .NET 7.1" >
         < meta  name ="CODE_LANGUAGE"  Content ="C#" >
         < meta  name ="vs_defaultClientScript"  content ="JavaScript" >
         < meta  name ="vs_targetSchema"  content ="http://schemas.microsoft.com/intellisense/ie5" >
     </ HEAD >
     < body  MS_POSITIONING ="GridLayout" >
         < form  id ="Form1"  method ="post"  runat ="server" >
             < FONT  face ="宋体" >
                 < asp:ListBox  id ="ListBox1"  style ="Z-INDEX: 101; LEFT: 352px; POSITION: absolute; TOP: 272px"
                    runat ="server"  AutoPostBack ="True" >
                     < asp:ListItem  Value