public string Execute(IEnumerable <string> parameters) { IList <string> args = parameters.ToList(); if (args.Count != 4) { throw new InvalidBookServiceParametersExeption("Invalid numbers of parameters"); } string title = args[0]; string genre = args[1]; string author = args[2]; string bookInStore = args[3]; var newGenre = genreServices.AddGenre(genre); var newAuthor = authorServices.AddAuthor(author); var addedBook = booksServices.AddBook(title, newGenre, newAuthor, bookInStore); return($"New book {addedBook.Title} was added."); }