using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Book b1 = new Book("book1", 554654, "Mathematics", Convert.ToDateTime("04/01/2015 7:32:47 AM"));

​

Book b2 = new Book("book2", 454654, "English", Convert.ToDateTime("04/05/2015 8:32:47 AM"));

​

Book b3 = new Book("book3", 754654, "English", Convert.ToDateTime("04/03/2015 7:32:47 AM"));

​

Book b4 = new Book("book4", 854654, "History", Convert.ToDateTime("04/05/2015 9:32:47 AM"));

​

Book b5 = new Book("book5", 154654, "Mathematics", Convert.ToDateTime("04/01/2015 7:32:47 AM"));

​

Book b6 = new Book("book6", 354654, "History", Convert.ToDateTime("04/03/2015 8:32:47 AM"));

​

List<Book> booklist = new List<Book> { b1, b2, b3, b4, b5, b6 };

        IEnumerable<IGrouping<int, Book>> booklistgroups = booklist.GroupBy(b => b.purchaseDate.Hour);

​

foreach (IGrouping<int, Book> bookgroup in booklistgroups)

​

{

​

Console.Write("\nBooks in " + bookgroup.Key +" category: " + bookgroup.Count().ToString());

​

foreach (Book book in bookgroup)

​

{

​

Console.Write(book.name+" ");

​

}

​

}

    }

​

​

​

    class Book

    {

        public DateTime purchaseDate;

        public string name;

        public int isbn;

        public string category;

        public Book(string name, int isbn, string category, DateTime d)

        {

            this.name = name;

            this.isbn = isbn;

            this.category = category;

            this.purchaseDate = d;

        }

    }

}