Using UpdatePanels Inside A Repeater On A Content Page

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In my previous post, I described how to use an UpdatePanel that is located inside a Repeater or other data-bound control while maintaining your databinding. In addition to the data-binding challenge, dynamically creating UpdatePanels your page can also pose other complications.

Another issue that I’ve encountered is identifying controls that the AsyncPostBackTrigger on the UpdatePanel refer to if you are using master pages. So long as the control you are trying to trigger on is located in the same Content control of the content page, everything works just fine. However, if the UpdatePanel is located in one Content control while the control that triggers the asynchronous postback is in another UpdatePanel, you’ll get an exception when the page is loaded saying that it couldn’t find a control with the ID you specified.

I’ve found various solutions for correcting this problem by dynamically adding the trigger in code, and using the control’s UniqueID to identify it. However, this becomes significantly more complicated when you are dealing with a dynamically added control. The best solution I’ve found so far is to use ScriptManager.RegisterAsyncPostBackControl to register the post back, and manually call Update on each UpdatePanel to perform the update. Below is the code that I’ve found fixes the problem.

Partial Public Class _Default
    Inherits System.Web.UI.Page

    Dim DateUpdatePanels AS New List(Of UpdatePanel)

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        ScriptManager.GetCurrent(Me).RegisterAsyncPostBackControl(edtDate)
        DataBind()
    End Sub

    Private Sub Repeater_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles Repeater.ItemDataBound
        Dim pnl As UpdatePanel = e.Item.FindControl("upnlShowTimes")
        If Not IsNothing(pnl) Then
            DateUpdatePanels.Add(pnl)
        End If
    End Sub

    Private Sub edtDate_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles edtDate.TextChanged
        For Each pnl As UpdatePanel In DateUpdatePanels
            pnl.Update()
        Next
    End Sub

End Class

Note that if you define your ScriptManager on your content page instead of the master page, you can refer to it directly instead of using ScriptManager.GetCurrent(Me). Also, you must be sure to set UpdateMode to Conditional on each UpdatePanel.

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