＆＃39; HoverMenuExtender2＆＃39;的TargetControlID无效。 ID为＆＃39; cable＆＃39;无法找到

Question

当我将列ID应用到Hovermenuextender的targetconrtolID时，它无效并且出现错误

'HoverMenuExtender2'的TargetControlID无效。找不到ID为“cable”的控件。

我需要在结尾的列

上显示我的子菜单

编写的代码在这里

<cc1:HoverMenuExtender ID="HoverMenuExtender2" runat="server" PopupControlID="ProjectMenu" TargetControlID="cable" PopupPosition="Bottom" >
                            </cc1:HoverMenuExtender>


 <td align="center" style="border: medium solid White" class="style5" id="cable">
                            <asp:LinkButton ID="lblmenudashboard" runat="server" Font-Bold="False" Font-Underline="False"
                                ForeColor="white" OnClick="lblmenudashboard_Click">Dashboard</asp:LinkButton>
                        </td>

<asp:Panel ID="ProjectMenu" runat="server" Visible="true" Width="210px">
                                <table cellpadding="0" cellspacing="0" class="style8" align="center">
                                    <tr>
                                        <td align="center">
                                            <asp:LinkButton ID="lblsubMenu_Star" runat="server" Font-Bold="False" Font-Underline="False"
                                                ForeColor="white"> Project0</asp:LinkButton>
                                        </td>
                                    </tr>
                                    <tr>
                                        <td align="center">
                                            <asp:LinkButton ID="lblsubMenu_Udaan" runat="server" Font-Bold="False" Font-Underline="False"
                                                ForeColor="white"> Project1</asp:LinkButton>
                                        </td>
                                    </tr>
                                </table>
                            </asp:Panel>

我已经应用了scriptManager。另请告诉我如何选择hovermenu以便我可以打开它们自己的标签。