/// <summary>
 /// Finds a Book object that has the same exact ISBN as the string passed in the argument
 /// </summary>
 /// <param name="isbn">isbn string used to search Books</param>
 /// <returns>Book that matches the ISBN string exactly</returns>
 public Book SearchISBN(string isbn)
 {
     return(bookInventory.SearchByISBNExact(isbn));
 }