How can I update an UpdatePanel in a control from the page?

I have a modal on a page that also contains a user control.

When clicking the 'OK' button in the modal, I would like to update an UpdatePanel that is contained within the user control on the page.

Currently the 'OK' button on the modal does a full page postback, I'd like to just update the panel, but I'm not sure how to add it as a trigger since it's not in the control the UpdatePanel is.

Thanks.

I have a partial answer... I can update the panel once by doing this:

Dim addTrigger As New AsyncPostBackTrigger
addTrigger.ControlID = MyButton.ID
addTrigger.EventName = "Click"
MyUserControl.GetUpdatePanel.Triggers.Add(addTrigger)

This will cause a partial post-back the first time, but after that first time it causes an entire page reload. Any ideas?

You can explicitly add the OK button as a AsyncPostBackTrigger for the UpdatePanel.

In the aspx markup for the UpdatePanel:

<asp:UpdatePanel ID="updPanel" runat="server">
    <ContentTemplate>
    ....
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="the control" EventName="Click" />
    </Triggers>
</asp:UpdatePanel>

or in the code-behind:

protected override void OnInit(EventArgs e)
{
    AsyncPostBackTrigger trigger = new AsyncPostBackTrigger();
    trigger.ControlID = "the Control";
    trigger.EventName = "Click";

    updPanel.Triggers.Add(trigger);

    base.OnInit(e);       
}