public string Execute(IEnumerable <string> parameters) { IList <string> args = parameters.ToList(); if (args.Count != 4) { throw new InvalidUserServiceParametersExeption("Invalid numbers of parameters"); } string firstName = args[0]; string middName = args[1]; string lastName = args[2]; string book = args[3]; var userWithBook = usersServices.BorrowBook(firstName, middName, lastName, book); return($"User {userWithBook.FirstName} " + $"borrow the book {book}"); }