asp.net ajax 1个按钮如何触发另外1个按钮啊？

我想点Button1的时候，提示是否更新表2，如果是，则触发Button2的Click事件。=================前台====================    <form id="form1" runat="server">
    <div>
   
        <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
            
        <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
            <ContentTemplate>    
                <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Button1" EventName="click" />
            </Triggers>
        </asp:UpdatePanel> 
              
        <asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="false">
            <ContentTemplate>       
                <asp:Button ID="Button2" runat="server" Text="Button" OnClick="Button2_Click" />
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Button2" EventName="click" />
            </Triggers>
        </asp:UpdatePanel>
                
    </div>
    </form>function A()
{
    if(confirm("表1更新完毕！是否更新另表2"))
    {
        document.getElementById("Button2").click();        
    }
}function B()
{
    alert("表2更新完毕!");
}</script>====================后台===============  protected void Button1_Click(object sender, EventArgs e)
    {
        //更新表1操作
        ScriptManager.RegisterClientScriptBlock(UpdatePanel1, UpdatePanel1.GetType(), "sysinfo", "A();", true);
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
        //更新表2操作
        ScriptManager.RegisterClientScriptBlock(UpdatePanel2, UpdatePanel2.GetType(), "sysinfo", "B();", true);
    }========================================我点了Button1，在弹出的提示 点确定 为什么没有弹出  "表2更新完毕"  的提示信息啊希望高手指点