Public MustInherit Class BasisControl
    Inherits UserControl
 
    MustOverride Sub TuEtwas()
 
End Class
 
Public Class Control_A
    Inherits BasisControl
 
    Public Overrides Sub TuEtwas()
        MessageBox.Show("A")
    End Sub
 
End Class
 
Public Class Control_B
    Inherits BasisControl
 
    Public Overrides Sub TuEtwas()
        MessageBox.Show("B")
    End Sub
 
End Class
 
Public Class Form1
 
    Dim Ctr_1 As BasisControl = New Control_A
    Dim Ctr_2 As BasisControl = New Control_A
 
    Sub Vertauschen()
 
        Dim temp As BasisControl
 
        temp = Ctr_1
        Ctr_1 = Ctr_2
        Ctr_2 = temp
 
    End Sub
 
End Class