tp1Entity/tp1/Library/Entities/BookEntity.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Library.Entities
{
    public class BookEntity
    {
        public int ID { get; set; }
        public string Title { get; set; }
        public string Author { get; set; }
        public string Isbn { get; set; }

        public BookEntity(string title, string author, string isbn) { 
            Title = title;
            Author = author;
            Isbn = isbn;
        }
    }
}