Sieve Of Eratosthenes (C#)

program.cs

var primes = SieveOfEratosthenes(100);

var primes_ = string.Join(',', primes);

Console.WriteLine(primes_);

int[] SieveOfEratosthenes(int n)
{
  bool[] noPrime = new bool[n];

  for (int p = 2; p * p < noPrime.Length; ++p)
  {
    if (!noPrime[p])
    {
        for (int i = 2*p; i < noPrime.Length; i += p)
        {
            noPrime[i] = true;
        }
    }
  }

  var result = new List<int>(noPrime.Length);
  for (var i = 2; i < noPrime.Length; ++i) 
  {
    if (!noPrime[i])
    {
      result.Add(i);
    }
  }

  return result.ToArray();
}