public IEnumerable <Comment> ReadCommentByFile(string id) { int rightId; if (Int32.TryParse(id, out rightId)) { if (_fileDao.GetFileById(rightId) != null) { return(_commentDao.ReadCommentByFile(rightId).ToList()); } else { Console.WriteLine("Can't find file"); return(null); } } else { Console.WriteLine("Incorrect ID (not number)"); return(null); } }