Question

I’ve never taken the initiative to learn the correct class modifier since it has always been a “nice to have” but not a “need to have”.

It annoys me that I can do Dim F as New Person.FavoriteFoodsList.

Which class modifier do I use so that my Person class can utilize the FavoriteFoodsList but nothing outside of Person can instantiate the FavoriteFoodsList?

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim P As New Person
    P.FavoriteFoods.Add("Pizza")
    Dim F As New Person.FavoriteFoodsList 'How do I prevent this
End Sub
Public Class Person
    Public FavoriteFoods As New FavoriteFoodsList
    Public Class FavoriteFoodsList
        Inherits Collections.Generic.List(Of String)
    End Class
End Class

Answer 1

I recommend you define a public interface for your class then mark the implementation as private.

Public Interface IFavoriteFoodsList
    Inherits Collections.Generic.IList(Of String)
    ' Define other public api methods'
End Interface

Public Class Person
    Public FavoriteFoods As IFavoriteFoodsList = New FavoriteFoodsList
    Private Class FavoriteFoodsList
        Inherits Collections.Generic.List(Of String)
        Implements IFavoriteFoodsList
    End Class
End Class