From time to time we need to do something that the .Net framework doesn't immediately expose to us (without some finagling).  In this instance, I wanted to override the attributes that the labels generated by the CheckBoxList webcontrol.  However, I only wanted to modify this one instance of it.

In doing so, I needed to hook into the creation of the item collection of the CheckBoxList control, but I do not know of an event that we can use to do so.  So, I instead ran a loop through the controls collection to find the instances of the CheckBoxList control and make the changes I wanted. 

Here is an example:

Private Sub ReWriteCheckboxLabels()
     Dim ctl As System.Web.UI.Control
     Dim ctlCheck As WebControls.CheckBoxList
     ' loop through all of the controls in the UpdatePanel
     ' controls collection
     For Each ctl In Me.UpdatePanel1.Controls(0).Controls

          ' make sure that the current control is the right kind
          If ctl.GetType.ToString = 
               _"System.Web.UI.WebControls.CheckBoxList" Then

               ' yippee! it's a checkbox list - change the type
               ctlCheck = CType(ctl, WebControls.CheckBoxList)

               ' only do this if there are items to change
                Select Case ctlCheck.Items.Count
                    Case Is > 0
                         ' force the label text to inherit the 
                         ' correct class
                         Dim item As ListItem

                         ' loop through the items in the current 
                         ' checkbox list
                         For Each item In ctlCheck.Items
                              ' wrap the text within the label 
                              ' to override it's CSS class
                              item.Text = "<span class=""" & _
                                   "YOURCSSCLASSNAME"">" & _
                                   item.Text & "</span>"
                         Next
                    Case Else
                         'do nothing
               End Select
           End If
     Next
End Sub

In the previous example, I have at least one CheckBoxList control nexted within a MS AJAX UpdatePanel.  In order to get to the collection of controls, I need to first reference the controls using the
Controls collection of the first Controls instance in the UpdatePanel. 

If you are not nesting your controls a similar way, you can simply modify the first FOR EACH loop to be something more like this:

For Each ctl In Me.Controls

This would loop through all of the controls in the current page or user control.