I would like to verify something on maintaining a collection.

The collection is defined like this:

    Private oField As Collection = New Collection

I add items in a collection like this:

    ' Add a field in the collection
    ' expC1 Field
    Private Function AddField(ByVal tcField As String) As Boolean
        Dim lnKey As Integer = 0
        Dim loObject(3) As Object

        ' Initialization
        loObject(1) = tcField
        loObject(2) = True
        lnKey = oField.Count + 1
        loObject(3) = lnKey

        oField.Add(loObject, lnKey)

        Return True
    End Function

Then, in the code, based on some conditions, I may need to update an item in the collection. As we know, we cannot do that but to remove and add the item back in the collection. So, I usually do it like this:

        ' Get the list of fields missing from the dataset
        For Each loObject In oField

            ' Initialization
            lcField = loObject(1)
            lnKey = loObject(3)

            ' Logic here to determining if we have found it
            llFound = ...

            ' If we found it
            If llFound Then

                ' Remove this one from the collection
                oField.Remove(lnKey)

                ' Add the updated item in the collection
                loObject(2) = False
                oField.Add(loObject, lnKey)

            End If

        Next

While this has worked so far on pretty much everywhere I have used it, I discovered today that in a particular situation, it doesn't work. The problem relates to when adding the item back in the collection. On some of them, I get "Add failed. Duplicate key value supplied.".

We all know that the collection handling is a problem in .NET. The reason is because the second parameter, when adding an item in the collection, is known as the key. But, when adding or removing, we have to use an index. That approach has worked so far. It doesn't work today.

Anyone would have a better idea on updating an item in the collection?