Public Sub GenFunc(Of T As {Structure, System.IConvertible})(ByRef arg As T)
 
        'Überprüfung des Argumenttyps (Short ... ULong) über den Typecode 
        Dim tc As Integer = System.Type.GetTypeCode(GetType(T))
        If tc < 7 Or tc > 12 Then
            Throw New System.InvalidOperationException
        End If
 
        'Code der Funktion .........
        Dim erg As T
        '......
        '......
 
        arg = erg
    End Sub
 
    Public Sub GenFunc(Of T As {Structure, System.IConvertible})(ByRef arg As _
      T?)
        Dim iarg As T = Nothing
        If arg.HasValue Then iarg = arg.Value
        GenFunc(iarg)
        arg = iarg
    End Sub