public BookEntity GetBook(string bookTitle) 
        {
            BookEntity book = new BookEntity();
            foreach (BookEntity bookItem in _bookTable)
            {
                if (bookItem.BookTitle == bookTitle) 
                {
                    return bookItem;
                }            
            }

            return null;        
        }
 public bool RegisterBook(BookEntity newBookEntity) 
 {
     int idCounter = 1;
     foreach (BookEntity book in _bookTable)
     {
         if ((book.BookTitle == newBookEntity.BookTitle)&&(book.AuthorName == newBookEntity.AuthorName))
         {
             return false;
         }
         idCounter++;
     }
     newBookEntity.Id = idCounter;
     _bookTable.Add(newBookEntity);
     return true;
 }
 public bool RegisterBook(BookDto NewBook) 
 {
     BookEntity bookEntity = new BookEntity();
     bookEntity.BookTitle = NewBook.BookTitle;
     bookEntity.AuthorName = NewBook.AuthorName;
     if (_dblibrary.RegisterBook(bookEntity))
     {
         //Console.ForegroundColor = ConsoleColor.DarkYellow;
         //Console.WriteLine("LibraryService - Libro creado correctamente\n");
         //Console.ForegroundColor = ConsoleColor.White;
         return true;
     }
     else 
     {
         //Console.ForegroundColor = ConsoleColor.DarkYellow;
         //Console.WriteLine("LibraryService - El libro no se ha creado en el sistema\n");
         //Console.ForegroundColor = ConsoleColor.White;
         return false;
     }
 }