private void backBtn_Click(object sender, RoutedEventArgs e)
        {
            OrderListWindow olw = new OrderListWindow();

            olw.Show();
            this.Close();
        }
        private void AddOrder_Click(object sender, RoutedEventArgs e)
        {
            ProxyOrder proxyOrder = new ProxyOrder(FirstnameTextBox.Text, LastnameTextBox.Text, PeselTextBox.Text);
            Order      order      = proxyOrder.Validate(chosenProducts);

            if (order != null)
            {
                foreach (IProduct product in chosenProducts)
                {
                    data.decrementCountProduct(product.Id, product.Count);
                }

                data.addOrder(order, chosenProducts);
                order.OrderId = data.getLastInsertProductId();

                Order o = data.getOrder(order.OrderId);

                Console.WriteLine(o.getTotalCost());

                // Discount handlers
                if ((bool)regularCustomerCheckBox.IsChecked == true)
                {
                    o = new RegularCustomerDecorator(o);
                }
                if ((bool)xmasSaleCheckBox.IsChecked == true)
                {
                    o = new ChristmasSaleDecorator(o);
                }
                data.updateOrderTotalCost(order.OrderId, o.getTotalCost());


                OrderListWindow olw = new OrderListWindow();
                olw.Show();
                this.Close();
            }
            else
            {
                MessageBox.Show("Imie i nazwisko nie powinno być puste, PESEL musi składać się z 11 cyfr oraz lista produktów nie może być pusta", "Alert", MessageBoxButton.OK, MessageBoxImage.Information);
            }
        }