Func<int> readNumber = () =>
            {
                int number;
                while (!int.TryParse(Console.ReadLine(), out number))
                    writeLn("Invalid format, try again");

                return number;
            };

 while (true)
            {
                collectionLength = readNumber();
                const int MAX_LENGTH = 5;
                if (collectionLength > 0 && collectionLength <= MAX_LENGTH)
                    break;

                writeLn(string.Format("Number should be between 0 and {0}. Please try again", MAX_LENGTH));
            }