[VB.net] object v dataset column

A kdo ve zakaj se ne da shranit dataset v datoteko, če je v dataset column z objektom?

Zadeva se pa obnaša tako, da prvič lahko shranim. Potem ko naredim load v dataset in ko probam ponovno shranit mi napiše to napako... V čem je fora?

    Public Sub Loaddataset(file As String)
        If IO.File.Exists(file) Then
            Dim fs As New Compression.GZipStream(New FileStream(file, FileMode.Open), Compression.CompressionMode.Decompress)
            Dim bf As BinaryFormatter = New BinaryFormatter()
            DataSet1 = CType(bf.Deserialize(fs), Data.DataSet)
            fs.Close()
        End If
    End Sub

    Public Sub Savedataset(file As String)
        If IO.File.Exists(file) = True Then
            IO.File.Delete(file)
        End If
        Dim fs As New Compression.GZipStream(New FileStream(file, FileMode.Create), Compression.CompressionMode.Compress)
        Dim bf As BinaryFormatter = New BinaryFormatter()
        bf.Serialize(fs, DataSet1)
        fs.Close()
    End Sub