Esempio di astrazione [VB .NET]

Public MustInherit Class A
   Public MustOverride Sub F()
End Class
Public MustInherit Class B : Inherits A
    Public Sub G()
       ..........
    End Sub
End Class
Public Class C : Inherits B
   public Overrides Sub F()
      ' Implementazione del metodo F
      ..........
   End Sub
End Class