private void BtnEdit_Click(object sender, RoutedEventArgs e)
        {
            Aircompany selectedCompany = (Aircompany)DGAircompany.SelectedItem;

            if (SelectedAircompany(selectedCompany))
            {
                Aircompany           oldAircompany = selectedCompany.Clone() as Aircompany;
                EditAircompanyWindow edw           = new EditAircompanyWindow(selectedCompany, EditAircompanyWindow.Option.EDIT);
                if (edw.ShowDialog() != true)
                {
                    int index = IndexOfSelectedAircompany(selectedCompany.Id);
                    Data.Instance.Aircompanies[index] = oldAircompany;
                }
                else
                {
                    selectedCompany.Change();
                }
            }
        }
        private void BtnAdd_Click(object sender, RoutedEventArgs e)
        {
            EditAircompanyWindow edw = new EditAircompanyWindow(new Aircompany(), EditAircompanyWindow.Option.ADDING);

            edw.ShowDialog();
        }