ProjectLib/ProjectLibrary/Forms/FOrder.cs

using ProjectLibrary.Repositories;
using ProjectLibrary.Entites;
using System.Xml.Linq;

namespace ProjectLibrary.Forms
{
    public partial class FOrder : Form
    {
        private readonly IOrderRepository _orderRepository;
        private int? _orderId;

        public FOrder(IOrderRepository orderRepository)
        {
            InitializeComponent();
            _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));         
        }

        public int Id
        {
            set
            {
                try
                {
                    var order = _orderRepository.ReadOrderById(value);
                    if (order == null)
                    {
                        throw new InvalidOperationException("Заказ не найден.");
                    }

                    txtOrderDate.Text = order.OrderDate.ToString();
                    txtReturnDate.Text = order.ReturnDate.ToString();
                    comboBox.SelectedItem = order.ReaderID;
                    dataGridViewBook.DataSource = order.BookOrders;
                    _orderId = value;
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "Ошибка при загрузке данных", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
        }

        private List<Book_Orders> CreateListBooksFromDataGrid()
        {
            var list = new List<Book_Orders>();
            foreach (DataGridViewRow row in dataGridViewBook.Rows)
            {
                if (row.Cells["ColumnBook"].Value == null)
                {
                    continue;
                }
                list.Add(Book_Orders.CreateEntity(0, Convert.ToInt32(row.Cells["ColumnBook"].Value)));
            }
            return list;
        }

        private void ButtonSave_Click(object sender, EventArgs e)
        {
            try
            {
                if (string.IsNullOrWhiteSpace(txtOrderDate.Text) || string.IsNullOrWhiteSpace(txtReturnDate.Text) || comboBox.SelectedItem == null)
                {
                    throw new Exception("Не все поля заполнены.");
                }

                var order = Orders.CreateEntity(
                    _orderId ?? 0,
                    DateTime.Parse(txtOrderDate.Text),
                    DateTime.Parse(txtReturnDate.Text),
                    int.Parse(comboBox.SelectedItem.ToString()),
                    CreateListBooksFromDataGrid()
                );

                if (_orderId.HasValue)
                {
                    _orderRepository.UpdateOrder(order);
                }
                else
                {
                    _orderRepository.CreateOrder(order);
                }
                Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Ошибка при сохранении данных", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void ButtonCancel_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}