A C# implementation of the Sieve of Eratosthenes algorithm.

SieveOfEratosthenes.cs

namespace SieveOfEratosthenes
{
    class SieveOfEratosphenes
    {
        public static void printPrimesUntil(int n)
        {
            List<int> primes = getPrimesUntil(n);
            printList(primes);
        }

        private static List<int> getPrimesUntil(int n)
        {
            bool[] primes = initialiseArrayOfSize(n);
            sieveNonPrimes(primes);
            return listFromPrimesSieve(primes);
        }

        private static bool[] initialiseArrayOfSize(int n)
        {
            bool[] primes = new bool[n + 1];
            for (int i = 0; i <= n; i++) { primes[i] = true; }
            return primes;
        }

        private static void sieveNonPrimes(bool[] primes)
        {
            for (int i = 2; i < Math.Sqrt(primes.Length); i++)
            {
                for (int p = i+i; p < primes.Length; p += i)
                {
                    primes[p] = false;
                }
            }
        }

        private static List<int> listFromPrimesSieve(bool[] primes)
        {
            List<int> primeList = new List<int>();
            for(int i=1; i<primes.Length; i++)
            {
                if(primes[i])
                {
                    primeList.Add(i);
                }
            }
            return primeList;
        }

        private static void printList(List<int> primes)
        {
            foreach(int prime in primes)
            {
                Console.Write(prime + ", ");
            }
            Console.WriteLine();
        }
    }
}