Struct1

namespace Library
{
    struct Book
    {
        public int ID;
        public string Title;
        public string ISBN;
        public DateTime ReleaseDate;
    }

    class Program
    {
        static void Main(string[] args)
        {
            Book book1;
            book1.ID = 1;
            book1.Title = "C# Series 1";
            book1.ISBN = "111";
            book1.ReleaseDate = DateTime.Now;

            Book book2;
            book2.ID = 2;
            book2.Title = "C# Series 2";
            book2.ISBN = "222";
            book2.ReleaseDate = DateTime.Now;

            Console.WriteLine("ID: {0} Title: {1} ISBN: {2} Release Date: {3}", book1.ID, book1.Title, book1.ISBN, book1.ReleaseDate);
            Console.WriteLine("ID: {0} Title: {1} ISBN: {2} Release Date: {3}", book2.ID, book2.Title, book2.ISBN, book2.ReleaseDate);
            Console.ReadKey();
        }
    }
}