How to get value from dynamic control on Post-back

Hi All,

This is my first post. The problem is about dynamic control.

1. In Page Load, I auto generated a datagrid.

 Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Dim lmws As New LIMSWSV10.LIMSService
        Dim ds As New DataSet
        If Not IsPostBack Then
            ds = lmws.GetResultValueForShippingJob(Request.QueryString("ShippingJobID"))
            dgResults.DataSource = ds
        end if
 End Sub
2. Then Item Data Bound check box column before each data column.
Private Sub dgResults_ItemDataBound(ByVal sender As System.Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles dgResults.ItemDataBound
        If (e.Item.ItemType = ListItemType.Item) Or (e.Item.ItemType = ListItemType.AlternatingItem) Then
            Dim i As Integer
            For i = 1 To (e.Item.Cells.Count - 1) Step 2
                e.Item.Cells(i).Controls.Add(New CheckBox)
        End If
    End Sub
3. How can I get my control to detect the checkbox checked event after post-back? * means that line meet problem.
Private Sub UpdateCofA()
        Dim lmws As New LIMSWSV10.LIMSService
        Dim resultcode As Integer
        Dim oncertificate As Boolean
        Dim dgitem As DataGridItem
        For Each dgitem In dgResults.Items
            Dim ckbox1, ckbox2, ckbox3 As CheckBox
            ‘can not pass from here.
            *ckbox1 = dgitem.Cells(1).Controls(0)
            *ckbox2 = dgitem.Cells(3).Controls(0)
            *ckbox3 = dgitem.Cells(5).Controls(0)
            If ckbox1.Checked = True Then
                oncertificate = True
                oncertificate = False
            End If
            resultcode = dgitem.Cells(8).Text
            lmws.UpdateResultOnCertificate(resultcode, oncertificate)
    End Sub
Actually, I cannot get my dynamic control any more. I'm looking forward to seeing your answer.
Thanks in advance!
8/23/2007 8:32:35 PM 72751 articles. 3 followers. Follow

6 Replies

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Any controls you create dynamically will retain their user selected/input values between postback, but they have to be re-created on postback. In your case, it looks like you are not adding the controls back when it's a postback.


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8/23/2007 8:56:21 PM

Please give more details.

8/23/2007 9:08:21 PM


Are you trying to detect when the user clicks a checkbox or are you trying to retain what was checked/unchecked between postbacks?



Please remember to click "Mark as Answer" on the posts that helped solve your issue.
8/23/2007 10:15:36 PM


Thank you for replying.  Actually, I'm trying to detect whick checkbox was checked when the user clicks a button. UpdateCofA is inside a button click method.   


8/24/2007 2:27:02 PM

Hi thewind,

Hopefully I haven't screwed you from getting an answer more quickly by members who are more experienced with the datagrid. I've done a lot with dynamic controls, though ;)

When you create a dynamic control during a Page_Load, any data changed by the user is retained between postbacks; asp handles that for you. However, you have to re-create the dynamic control when the page is posting back so that asp has a place to put the retained data. Usually, people place creation of the dynamic controls in the Page_Init event to ensure the control is present for data from the viewstate and postback to be loaded into the control. If I didn't explain that too well, check out msdn's asp page lifecycle article at

Simply put, you cannot exclude the code that creates your dynamic controls when a postback occurs. So, 

If Not IsPostBack Then
   'create my dynamic controls here
End If

will fail to retain your postback data because asp has nowhere to put it. You must be sure your dynamic controls are created everytime the page initializes/loads, regardless of a postback.

That being said, I don't know how you would handle that in the ItemDataBound event for the datagrid. If the only place you're binding your grid is when it's not a postback (which is how I read your source code), then I don't know how your dynamic checkboxes will retain their postback data.


Please remember to click "Mark as Answer" on the posts that helped solve your issue.
8/24/2007 4:38:25 PM

I did see a reference in this article to the ItemCreated event getting fired even during postback. Try moving your control creation there and see if it helps. (Number 4 in this article:



Please remember to click "Mark as Answer" on the posts that helped solve your issue.
8/24/2007 4:54:48 PM

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