更新面板必须缺少一些东西，但无法弄清楚是什么

<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<div id="Container" onclick="__doPostBack('UpdatePanel1', '');">
    <asp:UpdatePanel runat="server" ID="UpdatePanel1"
        OnLoad="UpdatePanel1_Load">
        <ContentTemplate>
            <asp:Label runat="server" ID="Label1" />
        </ContentTemplate>
    </asp:UpdatePanel>
</div>
</asp:Content>
<asp:Content runat="server" ID="BodyContent" Co