public static string PrintNextPrimeNumber(int currentHighest, List <int> primeNumbers, out int currentHighestUpdate) { //Again, making sure that the default value is the current highest prime. currentHighestUpdate = currentHighest; if (primeNumbers.Count == 0) { Message = "The list is empty, you must have at least one prime number in the list to use this function"; } else { int next = PrimeEvaluator.FindNextPrime(currentHighest); primeNumbers.Add(next); currentHighestUpdate = next; Message = $"The next prime number would be {next}. We have added it to the list"; } return(Message); }