asp.net - 模态弹出扩展器在 asp:content 中不起作用

Question

我在 asp:content 页面中有一个模态弹出扩展器。直到昨天它工作正常。我不确定我做了什么改变来打破它。如果有人能看到它并指出我正确的方向，我将不胜感激。

<asp:Content ID="Content5" ContentPlaceHolderID="sectioncontent" Runat="Server">
 <asp:Button ID="Button5" runat="server" Text="Show" />
 <ajaxToolkit:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="Button5" PopupControlID="Panel1" CancelControlID="Button1" >
                        </ajaxToolkit:ModalPopupExtender>
<asp:Panel ID="Panel1" runat="server" Height="65px"  >
    <p>
       The following records will be deleted from this Cluster</p>

 Comments:  <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox> <asp:Button ID="Button3" runat="server" 
            Text="Submit" onclick="Button3_Click" />
   <asp:Button ID="Button1" runat="server" 
            Text="Cancel" onclick="Button1_Click" />
</asp:Panel>

此外，当我单击“显示”按钮时，页面正在加载。