public void MyCode()
{
BookCatalog books = new BookCatalog();
books.Add(new Book("ISBN123", "War and Peace", "Tolstoj", 882));
books.Add(new Book("ISBN456", "It", "King", 587));
// books.AddBook(new Book("ISBN456", "It", "King", 587));
Catalog <int, DVD> dvds = new Catalog <int, DVD>();
dvds.Add(new DVD(17, "Heat", 153));
dvds.Add(new DVD(32, "Se7en", 110));
}