using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var book = new Book() {

            Chapters = { new Chapter() }

        };

        Console.WriteLine(book.Chapters.Count);

    }

    public class Chapter

{

    public int Id { get; set; }

    public string Title { get; set; }

}

​

    public class Book

    {

        public Book() { Chapters = new List<Chapter>(); }

        public int Id

        {

            get;

            set;

        }

​

        public string Category

        {

            get;

            set;

        }

​

        public string Title

        {

            get;

            set;

        }

​

        public IList<Chapter> Chapters

        {

            get;

            set;

        }

    }

}