AsyncPostBackTrigger for WebUserControl

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user-controls

asynchronous

Hi friends,
I created a Web UserControl.
Inside the web userControl i placed a Repeater.
Inside the repeater control contains
Label, Checkbox and UpdatePanel.
Inside the UpdatePanel i placed the Gridview.

When i checked the checkbox,i will dispaly a new column.
For that when i checked the check box it will show the particular grid datas only, remaining grid datas are cleared.
To solve this problem i added AsyncPostBackTrigger ControlID="chkShowRevisions" EventName="CheckedChanged"

<asp:Repeater ID="rptBatchWise" runat="server"

<ItemTemplate>

 <asp:Label ID="lblStage" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Name") %>' />
Show Last Date
<asp:CheckBox ID="chkShowRevisions" runat="server" AutoPostBack="true" OnCheckedChanged="chkShowRevision_CheckedChanged" />

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
    <asp:GridView ID="gv" runat="server" AutoGenerateColumns="false" >
    <Columns></Columns>
    </asp:GridView>
    </ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="chkShowRevisions" EventName="CheckedChanged" />
</Triggers>
    </asp:UpdatePanel>
</ItemTemplate>
</asp:Repeater>

Now the Problem is fixed.

In the parent page i called this usercontrol inside updatepanel.
Now again i'm facing this Problem.

How to solve this?
and How to add the AsyncPostBackTrigger in ParentPage.

</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="???" EventName="???" />
</Triggers>
    </asp:UpdatePanel>