Public Main()
    Dim o1 As New Derived_1 : o1.Initialize(New System.Windows.Forms.Button)
    Dim o2 As New Derived_2 : o2.Initialize(New System.Windows.Forms.Form)
    MsgBox(Convert.ToString(o1.GetType))
    If o1.Value Is Nothing Then MsgBox("Nothing") Else MsgBox(Convert.ToString( _
      o1.Value.GetType))
    o2.ASub(o1)
End Sub
 
Public MustInherit Class Base
  Public ReadOnly Property Value As System.Windows.Forms.Control
    Get
      Return Nothing
    End Get
  End Property
End Class
 
Public MustInherit Class Base(Of T As System.Windows.Forms.Control)
  Inherits Base
  Private VObject As T
  Public Sub Initialize(ByRef INPUT As T)
    If VObject Is Nothing Then VObject = INPUT
  End Sub
  Public Overloads ReadOnly Property Value As T
    Get
      Return VObject
    End Get
  End Property
End Class
 
Public Class Derived_1
  Inherits Base(Of System.Windows.Forms.Button)
End Class
 
Public Class Derived_2
  Inherits Base(Of System.Windows.Forms.Form)
  Public Sub ASub(Of T As Base)(ByRef INPUT As T)
    MsgBox(Convert.ToString(INPUT.GetType))
    If INPUT.Value Is Nothing Then MsgBox("Nothing") Else MsgBox( _
      Convert.ToString(INPUT.Value.GetType))
  End Sub
End Class