ajax日历不显示在子gridview中

Question

Ajax日历未在子GridView中显示

<asp:GridView ID="GVCollapse" runat="server">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:ImageButton ID="ImageButton1" runat="server"  OnClick="Show_Hide_ChildGrid" ImageUrl="~/images/plus.png" CommandArgument="Show" Height="20" Width="20" />  
                <asp:Panel ID="pnlOrders" runat="server" Style="display: none;">
                    <asp:GridView ID="gvOrders" runat="server">     
                        <asp:TemplateField HeaderText="Dispatch Date">
                            <ItemTemplate>
                                 <asp:TextBox Width="90px" ID="txtDispatchDate" runat="server" Text=""></asp:TextBox>
                                 <ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server" Format="dd/MM/yyyy"
                                    PopupButtonID="txtDispatchDate" TargetControlID="txtDispatchDate">
                                 </ajaxToolkit:CalendarExtender>
                            </ItemTemplate>
                        </asp:TemplateField>        
                    </asp:GridView>
                </asp:Panel>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Ajax Calendar在子gridview中不起作用，而我用父gridview做同样的事情然后它运行良好 Ajax日历是不是与子gridview一起工作？或者我犯了任何错误。我发布了我的设计代码