Prime numbers

gistfile1.cs

    class Sieve
    {
        public static List<int> GetPrimeNumbers(int maxValue)
        {
            List<int> primeNumbers = new List<int>(new int[] { 2, 3, 5 });
            for (var testValue = primeNumbers.Max() + 1; testValue <= maxValue; testValue++)
            {
                int sqrtTestValue = (int)Math.Floor(Math.Sqrt(testValue));

                bool isPrime = true;
                foreach (var primeNumber in primeNumbers)
                {
                    if (primeNumber > sqrtTestValue)
                        break;
                    
                    if ((testValue % primeNumber) == 0)
                    {
                        isPrime = false;
                        break;
                    }
                }

                if (isPrime)
                    primeNumbers.Add(testValue);
            }

            return primeNumbers;
        }
    }