Trying to retrieve values in an UpdatePanel from the code behind

Question

I've got an asp.net web form, there is an update panel that contains a table with textboxes that the user enters values into. The table is in an updatepanel as the textboxes are generated from a very long running db query. It is generated a few seconds after the form loads using a timer control.

When the form is posted back the table isn't available to our code...

Here is the code for that section, this is a DynamicData edit page.

 <asp:UpdateProgress ID="UpdateProgress1" runat="server" 
            AssociatedUpdatePanelID="UpdatePanel2">
            <ProgressTemplate>
                <div>Getting subjects...</div>
            </ProgressTemplate>
        </asp:UpdateProgress>
        <asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Conditional"  >
            <ContentTemplate>
                <asp:Timer ID="Timer1" runat="server" Interval="2000" Enabled="false" >
                </asp:Timer>
                <div id="subjects_fav">
                    <asp:Table ID="tabSubjectsFav" runat="server" BorderWidth="2" BorderColor="Aquamarine">
                    </asp:Table>
                </div>

            <asp:Button ID="UpdateButton" runat="server" OnClick="SaveEverything" Text="Save Everything" />

            </ContentTemplate>
        </asp:UpdatePanel>


Protected Sub Page_Init(ByVal sender As Object, ByVal e As EventArgs)
    'DynamicDataManager1.RegisterControl(DetailsView1)
    DynamicDataManager1.RegisterControl(lvArticles1)
    DynamicDataManager1.RegisterControl(lvArticles2)
    DynamicDataManager1.RegisterControl(lvArticles3)
    DynamicDataManager1.RegisterControl(lvArticles4)
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    'trying to get the id_project for this page
    'get article id for first article

    If Not IsPostBack Then
        Timer1.Enabled = True
    Else
        UpdatePanel2.Update()
    End If

    'now get related project from db
    Dim db As New MTRData.mtddDataContext()
    Dim art = (From a In db.articles _
                 Where a.id = Request.QueryString("id") Take 1 _
                 Select a).SingleOrDefault()
    'txtid_project.Text = art.id_project

    'need to use this all over the place so saving it as a property type thing as well
    _ProjectID = art.id_project
    _PublicationID = art.id_publication
    _ArticleID = art.id

End Sub

Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick

    If boolTimerFired = False Then
        Timer1.Enabled = False
        boolTimerFired = True
        GenerateSubjectsFavGrid(_ArticleID)
        UpdatePanel2.Update()
    End If
    Timer1.Enabled = False

End Sub

Answer 1

Can't really diagnose this without some code. I'm guessing that you're generating the textboxes in the wrong part of the page lifecycle though. If you're not doing it during OnInit(), and then rebuilding them in the same way on the submit, then there won't be any textboxes on the form.

Remember that each new postback creates a new page object with a fresh new set of control instances. If your dynamic controls aren't created the same way each time, then they just won't be there.