javascript - AJAX 工具包 ConfirmButtonExtender 未打开确认窗口

Question

我无法在单击按钮时触发确认。ASP页面顶部有注册：

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %>

这是代码：

<asp:Button ID="btnGetSelectedReports" runat="server" 
    Text="Download Selected Report(s)" 
    OnClick="btnGetSelectedReports_Click" BackColor="#337AB7" 
    ForeColor="White" Width="500px" Height="36px" Font-Bold="True" 
    Font-Size="Medium" />      
<asp:ConfirmButtonExtender ID="btnGetSelectedReports_ConfirmButtonExtender" 
    runat="server" 
    BehaviorID="btnGetSelectedReports_ConfirmButtonExtender" 
    ConfirmText="The selected report(s) will be written to your folder. Do you wish to continue?" 
    TargetControlID="btnGetSelectedReports" 
    OnClientCancel="btnClearAll_Click()">
</asp:ConfirmButtonExtender>

在 web.config 文件中：

<controls>
    <add tagPrefix="ajaxtoolkit" namespace="AjaxControlToolkit" assembly="AjaxControlToolKit"/>
</controls>

当然，我添加了脚本管理器：

<asp:ScriptManager ID="ScriptManager" runat="server" EnablePageMethods="true">
</asp:ScriptManager>>

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