private void AvailableSalesmanListView_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if ((sender as ListView).SelectedItem is Salesman item)
            {
                Salesman salesman = new Salesman
                {
                    salesman_ID = item.salesman_ID,
                    name        = item.name,
                };

                District selectedDistrict = (District)districtListView.SelectedItem;

                DistrictsController.AddSecondarySalesman(selectedDistrict.district_ID, item.salesman_ID);

                List <Salesman>[] salesmen = DistrictsController.GetSecondarySalesmenForDistrict(selectedDistrict.district_ID);

                secondarySalesmanListView.ItemsSource = null;
                availableSalesmanListView.ItemsSource = null;

                secondarySalesmanListView.Items.Clear();
                availableSalesmanListView.Items.Clear();


                secondarySalesmanListView.ItemsSource = salesmen[0];
                availableSalesmanListView.ItemsSource = salesmen[1];
            }
        }
        private void DistrictListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if ((sender as ListView).SelectedItem is District item)
            {
                storeListView.ItemsSource = DistrictsController.GetStoresForDistrict(item.district_ID);

                List <Salesman>[] secondarySalesmen = DistrictsController.GetSecondarySalesmenForDistrict(item.district_ID);
                secondarySalesmanListView.ItemsSource = secondarySalesmen[0];
                availableSalesmanListView.ItemsSource = secondarySalesmen[1];


                List <Salesman>[] responsibleSalesmen = DistrictsController.GetResponsibleSalesmenForDistrict(item.district_ID);

                responsibleSalesmanListView.ItemsSource       = responsibleSalesmen[0];
                ChooseResponsibleSalesmanComboBox.ItemsSource = responsibleSalesmen[1];
            }
        }