Pass-through methods vs. accessing nested objects directly - vb.net

Question

What I have is an object that contains a list of objects that each contain another list of objects that have properties and such.
Currently I use pass-through methods to be able to add to those nested objects, like in this extremely simplified example:
Public Class clsA
Private objB As List(Of clsB) = New List(Of clsB)
Public Sub New()
objB.Add(New clsB)
End Sub
Public Sub AddInt(ByVal BIndex As Int32, ByVal CIndex As Int32, ByVal Number As Int32)
objB(BIndex).AddInt(CIndex, Number)
End Sub
End Class
Public Class clsB
Private objC As List(Of clsC) = New List(Of clsC)
Public Sub New()
objC.Add(New clsC)
End Sub
Public Sub AddInt(ByVal CIndex As Int32, ByVal Number As Int32)
objC(CIndex).AddInt(Number)
End Sub
End Class
Public Class clsC
Private lstNum As List(Of Int32) = New List(Of Int32)
Public Sub AddInt(ByVal Number As Int32)
lstNum.Add(Number)
End Sub
End Class
It seems like proper coding standards would tell me this is correct compared to:
Public Class clsD
Public objE As List(Of clsE) = New List(Of clsE)
Public Sub New()
objE.Add(New clsE)
End Sub
End Class
Public Class clsE
Public objF As List(Of clsF) = New List(Of clsF)
Public Sub New()
objF.Add(New clsF)
End Sub
End Class
Public Class clsF
Public lstNum As List(Of Int32) = New List(Of Int32)
End Class
Are there some instances where either method would be acceptable? Or would the pass-through setup always be preferred?
Public Class Form1
Dim oA As clsA = New clsA
Dim oD As clsD = New clsD
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
oA.AddInt(0, 0, 3)
oD.objE(0).objF(0).lstNum.Add(3)
End Sub
End Class

Answer 1

Think about how it's done throughout the .NET Framework. The collection should be assigned to a private field and exposed via a public read-only property.
Public Class Thing
Private _stuff As New List(Of Thing)
Public ReadOnly Property Stuff() As List(Of Thing)
Get
Return _stuff
End Get
End Property
End Class
The caller can then access the collection directly to call its Add method, etc, but cannot assign a whole new collection. There are examples everywhere: Control.Controls, ListBox.Items, ComboBox.Items, ListView.Items, DataSet.Tables, DataSet.Relations, DataTable.Rows, Datatable.Columns, etc, etc, etc.