ProjectLib/ProjectLibrary/Entites/Orders.cs

using DocumentFormat.OpenXml.Office2010.Excel;
using Microsoft.VisualBasic;
using ProjectLibrary.Entities;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ProjectLibrary.Entites
{
    public class Orders
    {
        public int Id { get; private set; }

        [DisplayName("Дата взятия книги")]
        public DateTime OrderDate { get; private set; }

        [DisplayName("Дата зврата книги")]
        public DateTime ReturnDate { get; private set; }

        [DisplayName("Идентификационный номер читателя")]
        public int ReaderID { get; private set; }

        public string BookName {  get; set; }

        [Browsable(false)]
        public IEnumerable<Book_Orders> BookOrders
        {
            get;
            private set;
        } = [];

        [DisplayName("Отданные книги")]
        public string BookOrdersing => BookOrders != null ?
            string.Join(", ", BookOrders.Select(x => $"{x.BookID}({x.Count})")) :
            string.Empty;

        public static Orders CreateEntity(int id, DateTime returnDate, int readerID, IEnumerable<Book_Orders> bookOrders)
        {
            return new Orders
            {
                Id = id,
                OrderDate = DateTime.Now,
                ReturnDate = returnDate,
                ReaderID = readerID,
                BookOrders = bookOrders
            };
        }
        public void SetOrdersOfBooks(IEnumerable<Book_Orders> book_Orders)
        {
            if (book_Orders != null && book_Orders.Any())
            {
                BookOrders = book_Orders;
            }
        }
    }
}