I created a user control which has a imagebuttton in it, I then exposed the click event of the button to the page the user control was placed on using the following code: 

    Public Event ImageButton1_Click(ByVal sender As Object, ByVal e As EventArgs)

    Private Sub eventXYZ(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles ImageButton1.Click
        RaiseEvent ImageButton1_Click(sender, e)
    End Sub

 I can use this event from the ASPX page with no problems, however when I use the event as an Atlas trigger for the updatepanel the page always posts back. Is there any way to wire this event up to the upatepanel and avoid the postback (btw the user control was not added dynamically).

Any chance you've found a resolution to this? I'm having the same issue but with a dropdown in a user control.....

 Thanks.

hello.

well, not something supported out of the box...maybe this tip will help you:

http://forums.asp.net/thread/1345407.aspx