BooksConsolapp/Books.ConsoleApp/Program.cs

using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Globalization;

namespace Books.ConsoleApp
{
    class Program
    {
        List<BooksByAuthor> BooksByAuthorCatalogue = null;
        static void Main(string[] args)
        {
            IEnumerable<Book> books = BookSource.Read();
            BooksByAuthorCatalogue = new List<BooksByAuthor>();

            foreach (var book in books)
            {
                if (AuthorIsAlreadyCataloged(book.author))
                {
                    // there are some(1 or more) books by this author already found and catalogued
                    var authorCatalogueIndex = LocateAuthorAlreadyCataloged(book.author);

                    var existingBooks = BooksByAuthorCatalogue[authorCatalogIndex].Books;
                    existingBooks.Add(book);
                }
                else
                {
                    CatalogueNewAuthor(book);
                }

            }

        }

        private static bool AuthorIsAlreadyCataloged(string author)
        {
            var authorAlreadyCatalogued = false;

            // we'll iterate over the catalogue to find the author - if athors's already been cataloged

            foreach (var entry in BooksByAuthorCatalogue)
            {
                if (entry.author == author)
                {
                    authorAlreadyCatalogued = true;
                    break;
                }
            }

            return authorAlreadyCatalogued;

        }

        private static int LocateAuthorAlreadyCataloged(string author)
        {
            var authorCatalogIndex = 0;

            // We'll iterate over the cataloge to find the author's index
            for (int j = 0; j < BooksByAuthorCatalogue.Count; j++)
            {
                var entry = BooksByAuthorCatalogue[j];
                if (entry.Author == author)
                {
                    authorCatalogIndex = j;
                    break;
                }
            }

        }

        private static void CatalogueNewAuthor(Book b)
        {
            // there are NONE books by this author already found and cataloged

            var newBookList = new List<Book> { b };
            var authorAndBooks = new BooksByAuthor(b.Author, newBookList);

            BooksByAuthorCatalogue.Add(authorAndBooks);
        }

        private static void OutputBooksByAuthor()
        {
            foreach (var ba in BooksByAuthorCatalogue)
            {
                Console.Write("Author: {0, -28} Books: ", ba.Author);
                foreach (var book in ba.Books)
                {
                    Console.Write(book.title + ", ");
                }
                Console.Write(Environment.NewLine);
            }
        }

    }

    public class BooksByAuthor
    {
        public readonly string Author;
        public readonly List<Book> Books;

        public BooksByAuthor(string author, List<Book> books)
        {
            Author = author;
            Books = books;
        }
    }

}