Removing and adding event handlers for different ComboBoxes where the ComboBox is passed as a parameter - vb.net

Question

I have a method that takes a ComboBox as a parameter and then adds data to it. When data is added, the SelectedIndexChangedEvent fires. Is there a way that, in the called method, I can remove the above event handler for whatever ComboBox is passed as a parameter and then add is at the end of the method? I know how to remove and add specific handlers, but can't figure out how to do it based on which ComboBox is passed.
Here's the method..
Private Sub PopulateComboBox(ByRef cboBox As ComboBox, ByVal itemSource As String)
'Remove handler for cboBox
'Do stuff that would otherwise cause the event handler to execute
'Add handler for cboBox
End Sub
I have 4 ComboBoxes - would it just be easier to remove all 4 event handlers and then add them again at the end of the code? I would however like to know if this is possible so that I can possibly apply to re-usable code in the future

Answer 1

The most basic way to go about this is to do this:
Private Sub PopulateComboBox(ByRef cboBox As ComboBox, ByVal itemSource As String)
RemoveHandler cboBox.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
'Do stuff that would otherwise cause the event handler to execute
AddHandler cboBox.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
End Sub
Another option, which might be better in some circumstances, is to do this:
Private _ignoreComboBox As ComboBox = Nothing
Private Sub PopulateComboBox(ByRef cboBox As ComboBox, ByVal itemSource As String)
_ignoreComboBox = cboBox
'Do stuff that would otherwise cause the event handler to execute
_ignoreComboBox = Nothing
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
If sender Is Not _ignoreComboBox Then
End If
End Sub
Or, to handle multiple combo boxes at the same time:
Private _ignoreComboBoxes As List(Of ComboBox) = New List(Of ComboBox)()
Private Sub PopulateComboBox(ByRef cboBox As ComboBox, ByVal itemSource As String)
_ignoreComboBoxes.Add(cboBox)
'Do stuff that would otherwise cause the event handler to execute
_ignoreComboBoxes.Remove(cboBox)
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
If Not _ignoreComboBoxes.Contains(DirectCast(sender, ComboBox)) Then
End If
End Sub

Answer 2

Here is one way:
' these happen to map to the same event handler
Private cb1Event As EventHandler = AddressOf cbx_SelectedIndexChanged
Private cb2Event As EventHandler = AddressOf cbx_SelectedIndexChanged
Then when used:
PopulateComboBox(cb1, items, cb1Event)
PopulateComboBox(cb2, items, cb2Event)
' or
PopulateComboBox(cb3, items, AddressOf cbx_SelectedIndexChanged)
The method would be declared:
Private Sub PopulateComboBox(cboBox As ComboBox,
items As String, ev As EventHandler)
Personally, since you know the cbo involved anyway, I'd do that before the call:
RemoveHandler cb1.SelectedIndexChanged, AddressOf cbx_SelectedIndexChanged
PopulateComboBox(cb1, items)
AddHandler cb1.SelectedIndexChanged, AddressOf cbx_SelectedIndexChanged
There is not much to be gained by passing all the info to do something to something else so it can do what you know needs to be done.