Solved

Loop through Controls in dynamic table inside place holder

Posted on 2009-07-10
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Last Modified: 2013-11-26
I am using vb.net. I have a place holder in a page that is populated by a dynamic table that is added to the place holder after the user selects a value from a drop down box. Inside this dynamic table are check boxes.

The goal is to cycle through these check boxes and figure out which ones are checked after a button is pushed. The problem seems to be when the html is rendered. I tried putting code in the init event. I have attached the code.
PH_Tables is the name of the place holder control. Inside that is a dynamic table that contains the check boxes. I included the function that returns the control causing the postback - for completeness.
Public Shared Function GetPostBackControl(ByVal page As Page) As Control
        Dim control As Control = Nothing
 
        Dim ctrlname As String = page.Request.Params.Get("__EVENTTARGET")
        If ctrlname <> Nothing And ctrlname <> String.Empty Then
            control = page.FindControl(ctrlname)
        Else
            Dim ctl As String
            For Each ctl In page.Request.Form
                Dim c As Control = page.FindControl(ctl)
                If TypeOf c Is System.Web.UI.WebControls.Button Then
                    control = c
                    Exit For
                End If
            Next
        End If
        Return control
    End Function
    Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
        Dim s As Control
        Dim cntrl As Control
        Dim cb_cntrl As CheckBox
        Dim SB_ext_desc As New StringBuilder
        Dim testme As String
 
        s = GetPostBackControl(Me)
 
        If (Not (IsNothing(s)) AndAlso s.ID = "Button1") Then
 
            For Each cntrl In PH_tables.Controls
                testme = cntrl.ID
                If TypeOf cntrl Is CheckBox Then
                    cb_cntrl = cntrl
                    If cb_cntrl.Checked = True Then
                        SB_ext_desc.Append(cntrl.ID)
                        SB_ext_desc.Append(" ")
                    End If
                End If
 
            Next
            Session("s_ext_desc") = SB_ext_desc
            Session("do_update") = True
        End If
 
    End Sub

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Question by:estanton
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5 Comments
 
LVL 12

Expert Comment

by:funwithdotnet
ID: 24828699
You  mention when, but not exactly _what_ the problem is.

I can guess that the dynamic control/table/etc. does not exist on postback. It has to be re-created or the control no longer exists on postback.
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Author Comment

by:estanton
ID: 24830458
Oops
I can not get to the check boxes. I have tried looping through the tabel and place holder controls in page init and pre render. The check boxes don't show up.
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LVL 12

Accepted Solution

by:
funwithdotnet earned 500 total points
ID: 24832294
If the checkboxes are in a dynamic table created in response to user input, they will not exist on future postbacks unless the action in response to the original user input is re-created. And if it has been re-created, it would not exist at Page_Init unless it is in a user control.

I'm not exactly sure what kind of control 'dynamic table' refers to. Perhaps the checkbox controls are not in the table, but in cell controls in row controls within the table. A recursive search is required.

Something like this:

Private Sub Page_Load( ...) 
  RecreateTableInPlaceHolder()
  FindMyControl(PlaceHolder)
End Sub
 
Private Sub FindMyControl(ByVal inputControl as Control)
  If inputControl = 'whatever you're looking for
    ' Do something.
  ElseIf inputControl.HasControls Then
    Dim myControl as Control
    For Each myControl in inputControl.Controls
      FindMyControl(myControl)
    Next
  End If
End Sub

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Author Comment

by:estanton
ID: 24836847
I will try that tomorrow.
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Author Comment

by:estanton
ID: 24844202
Worked great. Thanks! The checkbox was in the TableCell.
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