CollapsiblePanelExtender这Ajax控件

今天做考试系统是遇到一个问题从昨晚到今天才自己摸索出来 
ajax里面的CollapsiblePanelExtender控件控制Label显示文字（显示和隐藏）是呀设置Lable的AssociatedControlID属性为Label所在的Panel 
下面是示例代码： <asp:ScriptManager ID="ScriptManager1" runat="server"> 
        </asp:ScriptManager> 
        <cc1:CollapsiblePanelExtender ID="CollapsiblePanelExtender1" 
        TargetControlID ="Panel1" ExpandControlID ="Panel2" 
          CollapseControlID ="Panel2" 
          Collapsed ="true" 
           TextLabelID="Label1" 
            ExpandedText ="隐藏...." 
             CollapsedText ="显示...." 
            ImageControlID ="Image1" 
             
           ExpandedImage ="~/images/collapse_blue.jpg"         
            CollapsedImage ="~/images/expand_blue.jpg" 
           SuppressPostBack ="true" 
           SkinID ="CollapsiblePanelDemo" 
           runat="server"> 
         
        </cc1:CollapsiblePanelExtender> 
         
   <%-- <ajaxToolkit:CollapsiblePanelExtender ID="cpeDemo" runat="Server" 
        TargetControlID="Panel1" 
        ExpandControlID="Panel2" 
        CollapseControlID="Panel2" 
        Collapsed="True" 
        TextLabelID="Label1" 
        ImageControlID="Image1"     
        ExpandedText="(Hide Details...)" 
        CollapsedText="(Show Details...)" 
        ExpandedImage="~/images/collapse_blue.jpg" 
        CollapsedImage="~/images/expand_blue.jpg" 
        SuppressPostBack="true" 
        SkinID="CollapsiblePanelDemo" />--%> 
        <asp:Panel ID="Panel2" CssClass ="collapsePanelHeader" Height ="30px" Width ="100%" runat="server"> 
                 
         
         <div style="padding:5px; cursor: pointer; vertical-align: middle;"> 
                <div style="float: left;">What is ASP.NET AJAX?</div> 
                <div style="float: left; margin-left: 20px;"> 
                 
                    <asp:Label ID="Label1"  runat="server" AssociatedControlID="Panel1" >(haha....)</asp:Label> 
                </div> 
                <div style="float: right; vertical-align: middle;"> 
                    <asp:ImageButton ID="Image1" ImageUrl="~/Images/expand_blue.jpg" AlternateText="(Show Details...)" runat="server"/> 
                </div> 
            </div> 
            </asp:Panel> 
       <asp:Panel ID="Panel1" CssClass ="collapsePanel" Height ="0px" Width ="100%" runat="server"> 
         
         

            <p> 
                 
                <asp:ImageButton ID="Image2" runat="server" ImageUrl="~/Images/AJAX.gif" 
                    AlternateText="ASP.NET AJAX" ImageAlign="right" /> 
              哈哈o(∩_∩)o...哈哈 
            </p> 
       </asp:Panel>