Demo of SelectMany function

SelectManyExample.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace SelectManyExample
{
  public class BookCase
  {
    public List<string> Books { get; set; } = new List<string>();
  }

  class Program
  {
    static void Main(string[] args)
    {
      var BookCases = new List<BookCase>
      {
        new BookCase()
        {
          Books = new List<string>() { "The C Programming Language", "Writing a Compiler in Go", "The Little Schemer" }
        },
        new BookCase()
        {
          Books = new List<string>() { "How Linux Works", "Windows Via C/C++", "Structure and Interpretation of Computer Programs" }
        },
        new BookCase()
        {
          Books = new List<string>() { "Lisp in Small Pieces", "Programming Language Pragmatics", "Algorithms" }
        }
      };

      var books = BookCases.SelectMany(bc => bc.Books);

      foreach (var book in books)
        Console.WriteLine(book);
    }
  }
}