Hide the sort of a collection in VB.NET

Question

In the following example i would like to hide the .sort() method to the client, how could i achieve that ?

Namespace test
  Class Figure
    Implements IComparable(Of Figure)
    Public Property Area As Double
    Public Function CompareTo(ByVal other As Figure) As Integer Implements System.IComparable(Of Figure).CompareTo
      CompareTo = Me.Area.CompareTo(other.Area)
    End Function
  End Class
  Class Figures
    Inherits System.Collections.Generic.List(Of Figure)
    Public Shadows Sub Add(ByVal nieuweFiguur As Figure)
      MyBase.Add(nieuweFiguur)
      Me.Sort()
    End Sub
  End Class
  Class Client
    Public Shared Sub Main()
      Dim figures As New Figures
      figures.Add(New Figure With {.Area = 12})
      figures.Add(New Figure With {.Area = 16})
      '***********************************************************
      figures.Sort() 'i want to hide the sort method to the client
      '***********************************************************
    End Sub
  End Class
End Namespace

Answer 1

Quite simply, if you don't want a caller to be able to use an instance of your class as if it were an instance of the base class, you shouldn't have that inheritance relationship to start with - it breaks the Liskov Substitution Principle.

I strongly suspect that Figures should use composition instead of inheritance - so it would have a private field of List(Of Figure) instead of deriving from it, and you'd expose whichever operations you want to, and only those operations. Most operations could probably just delegate to the list.