Private Sub CaricaFileXML()
        RichTextBox1.Text = IO.File.ReadAllText(Application.StartupPath & "/Prova.xml")
        Ds2.ReadXml(Application.StartupPath & "/Prova.xml")
        ComboBox1.DataSource = Ds2.Tipologie.ToList
        ComboBox1.DisplayMember = "Tipologia"
        ComboBox1.ValueMember = "Id"
        'DataGridView1.Columns(0).Visible = False
        'DataGridView2.Columns(0).Visible = False
    End Sub
    Private Sub ComboBox1_SelectedValueChanged(sender As Object, e As System.EventArgs) Handles ComboBox1.SelectedValueChanged
        ComboBox2.DataSource = (From cat As DataSet1.CategorieRow In Ds2.Categorie
                                      Where cat.IdTipologia = DirectCast(ComboBox1.SelectedItem, DataSet1.TipologieRow).Id).ToList
        ComboBox2.DisplayMember = "Categoria"
    End Sub