updatepanel.update() 后网格视图不刷新

Question

在aspx中有如下网格设计

  <asp:UpdatePanel ID="UpdatePanel4" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
    <div style="overflow:scroll; width:auto;">
    <asp:GridView ID="grd_activities" runat="server" AutoGenerateColumns="False"  DataKeyNames="key_01" DataSourceID="SqlDataSource7" 
    EmptyDataText="No Activity Found" GridLines="Vertical" OnRowDataBound="grd_activities_databound" onrowcommand="grd_activities_RowCommand" 
    ShowFooter="True" Width="100%"  CssClass="GridViewStyle"  SelectedRowStyle-CssClass="sel" PagerStyle-CssClass="pgr" RowStyle-CssClass="rowHover" AutoPostBack="true">
    
    
    //grid column codes
    
    </ContentTemplate>
                                <Triggers>
            <asp:AsyncPostBackTrigger ControlID="Button2" > </asp:AsyncPostBackTrigger>
            <asp:AsyncPostBackTrigger ControlID="Button3"></asp:AsyncPostBackTrigger>
            <asp:AsyncPostBackTrigger ControlID="Button1"></asp:AsyncPostBackTrigger>
            <asp:AsyncPostBackTrigger ControlID="Button5"></asp:AsyncPostBackTrigger>
            <asp:AsyncPostBackTrigger ControlID="Button8"></asp:AsyncPostBackTrigger>
            <asp:AsyncPostBackTrigger ControlID="Grd_FailedActivity" > </asp:AsyncPostBackTrigger>
                                </Triggers>
                                </asp:UpdatePanel>

背后的代码

grd_activities.DataBind();
UpdatePanel4.Update();

但是网格在执行后没有更新。我在这里错过了什么？