Problem with Serialization XML (application WPF)

Imports System.Runtime.Serialization
Imports System.IO
Imports System.Xml.Serialization



<XmlRoot("DonneesLogiciel")> Public Class DataGeneraleAudit
    Public Sub New()

    End Sub
#Region "Déclaration"
    Public _DataTotale As List(Of DataAudit)
#End Region

#Region "Propiétés"
     <XmlAttribute("Total")> Public Property DonneeTotale() As List(Of DataAudit)
        Get
            Return _DataTotale
        End Get

        Set(ByVal value As List(Of DataAudit))
            _DataTotale = value
        End Set
    End Property

#End Region


End Class

Public Class DataAudit 


#Region "Declarations"
     Private _Technologie As New DataTechnologie
    Private _Acquisition As New DataAcquisition
    Private _Resultats As New DataResultats


#End Region

#Region "Propiétés"
     Public Property Technologie() As DataTechnologie
        Get
            Return _Technologie
        End Get

        Set(ByVal value As DataTechnologie)
            _Technologie = value
        End Set
    End Property


    Public Property Acquisition() As DataAcquisition
        Get
            Return _Acquisition
        End Get

        Set(ByVal value As DataAcquisition)
            _Acquisition = value
        End Set
    End Property

    Public Property ResultaAs As DataResultats
        Get
            Return _Resultats
        End Get

        Set(ByVal value As DataResultats)
            _Resultats = value
        End Set
    End Property

#End Region

#Region "Méthodes"
 
    Public Sub New()
   
    End Sub

#End Region

   
End Class

Public Class MainWindow
    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.

    End Sub
 Friend nomFichierConfigXml As String
    Friend Config As New DataGeneraleAudit

 Private Sub MainWindow_Closing(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing

        Try

            ' Sérialization XML...
            Dim xSerializer As XmlSerializer = New XmlSerializer(GetType(DataGeneraleAudit))
            Dim writer As TextWriter = New StreamWriter("nomFichierConfigXml")
            xSerializer.Serialize(writer, Config)
            writer.Close()

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub