FileUpload and UpdatePanel: ScriptManager.RegisterPostBackControl works the second time

Question

I\'m developing an ASP.NET application with C# and Visual Studio 2008 SP1. I\'m using WebForms.

I have an ASPX page with two UpdatePanels, one on the left that holds

Answer 1

In response to your second update,

I had this exact problem, and I believe it has to do with the fact that you are adding a dynamic control to your page inside of the UpdatePanel.

There may be a better way to do it out there, as I am certainly no ASP.NET expert, but I was able to solve this problem on my own by adding the control in a div that was hidden using CSS -before- it was needed, and then auto-incrementing the "dummy" control's ID so there are no conflicts, and I can keep adding as many as I want. That way, when the UpdatePanel is triggered it fully recognizes the controls and their contents, excepting the hidden ones of course.

I am using XSL to transform my XML into a dynamic page that includes ASP.NET controls, so essentially I did the following:

---

And then in the code-behind:

Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
    //Code to generate the data (stripped out because it is generated in a different manner than the original poster)

    //Add events for all of the new-found controls depending on their type
    recursiveAddEvents(nameOfPlaceHolder.Controls)
End Sub


//Add events for all of the new-found controls depending on their type
Sub recursiveAddEvents(ByRef controls As ControlCollection)
    For Each con As Control In controls
        If con.Controls.Count > 0 Then
            recursiveAddEvents(con.Controls)
        End If

        //Try to cast the control to different data types
        Dim btn As Button = TryCast(con, Button)
        Dim file As FileUpload = TryCast(con, FileUpload)

        //Test to see which type the control was and apply the actions to it
        If Not btn Is Nothing Then
            //Assign the correct click events
            If btn.Attributes.Item("action") = "addVersion" Then
                AddHandler btn.Click, AddressOf addDraftVersion
                btn.ID = btn.Attributes.Item("identity")

                //Register the control with the ScriptManager
                ScriptManager.GetCurrent(Page).RegisterPostBackControl(btn)
            End If
        ElseIf Not file Is Nothing Then
            //Assign the correct click events
            file.ID = file.Attributes.Item("identity")
        End If
    Next
End Sub

Protected Sub addDraftVersion(ByVal sender As Button, ByVal e As EventArgs)
    Dim fileName as String = sender.Attributes("title").Replace(" ", "_") & "_D" & info("draftID") & "_V" & info("versionID")
    Dim inputControl As FileUpload = TryCast(trackPH.FindControl(sender.Attributes("fileControlIdentity")), FileUpload)

    If inputControl Is Nothing Then
        Exit Sub
    End If

    //Do whatever need to be done

    //Trigger UpdatePanel(s)
    nameOfUpdatePanel.Update()
End Sub

---

I stripped out a lot of the code, but it should still get the general idea across :)