<System.Serializable()> _
Public Class X
    Dim i As Integer = 1
    Dim ii As Integer = 4
    Dim iii As Integer = 8
    <NonSerialized()> Private _pathToSave As String
    Sub New(ByVal pathToSave As String)
        _pathToSave = pathToSave
    End Sub
    Public Sub Speichern()
        Dim a As New Runtime.Serialization.Formatters.Binary.BinaryFormatter
        Dim b As New IO.FileStream(_pathToSave, IO.FileMode.Create)
        a.Serialize(b, Me)
        b.Close()
    End Sub
End Class
Public Class Y
    Dim a As X
    Sub New(ByVal pathToSave As String)
        a = New X(pathToSave)
    End Sub
    Public Sub Speichern()
        a.Speichern()
    End Sub
End Class

        Dim y As New Y("C:\data.dat")
        y.Speichern()