using System.Reflection; using System.Text; namespace Model { public class Book { private long id; public long Id { get { return id; } set { id = value;} } private string title; public string Title { get { return title; } set { title = value; } } private string author; public string Author { get { return author; } set { author = value; } } private string isbn; public string Isbn { get { return isbn; } set { isbn = value; } } public Book(long id, string title = "", string author = "", string isbn = "") { Id = id; Title = title; Author = author; Isbn = isbn; } public string Tostring(StringBuilder sb) { return Id.ToString() + " " + Title.ToString() + " " + Author.ToString() + " " + Isbn.ToString() ; } } }