private void _ordersBindingSource_PositionChanged(object sender, EventArgs e)
        {
            _orderDetailsBindingSource.DataSource =
                OrdersTestOperation.GetOrderDetailItems(((OrderItem)_ordersBindingSource.Current).OrderID);

            OrderDetailsDataGridView.DataSource = _orderDetailsBindingSource;
        }
        private async void OrdersWithNoDetailsButton_Click(object sender, EventArgs e)
        {
            var results = await OrdersTestOperation.GetOrdersWithoutOrderDetails();

            if (results.Count > 0)
            {
                MessageBox.Show($"Found {results.Count} orders with no details");
            }
        }
        private void GetOrdersForCustomer()
        {
            var currentCustomerIdentifier = ((CustomerItem)CustomersComboBox.SelectedItem).CustomerIdentifier;

            _ordersBindingSource.DataSource = OrdersTestOperation.GetCustomerOrders(currentCustomerIdentifier);


            OrderCountLabel.Text         = $"Order count: {_ordersBindingSource.Count}";
            OrderDataGridView.DataSource = _ordersBindingSource;

            if (_ordersBindingSource.Count == 0)
            {
                _orderDetailsBindingSource.DataSource = null;
                OrderDetailsDataGridView.DataSource   = null;
            }
            else
            {
                _orderDetailsBindingSource.DataSource = OrdersTestOperation
                                                        .GetOrderDetailItems(((OrderItem)_ordersBindingSource.Current).OrderID);
            }

            OrderDetailsDataGridView.DataSource = _orderDetailsBindingSource;
        }