Program.cs

using System;
using System.Collections.Generic;

namespace ConsoleApplication
{
    public class Program
    {
        private static void get_primes7(int n, List<int> res)
        {
            if (n < 2) return;
            if (n == 2)
            {
                res.Add(2);
                return;
            }

            List<int> s = new List<int>();
            for (int z = 3; z < n + 1; z += 2)
            {
                s.Add(z);
            }

            int mroot = (int)Math.Sqrt(n);
            int half = s.Count;
            int i = 0;
            int m = 3;
            while (m <= mroot)
            {
                if (s[i] != 0)
                {
                    int j = (int)((m * m - 3) * 0.5);
                    s[j] = 0;
                    while (j < half)
                    {
                        s[j] = 0;
                        j += m;
                    }
                }
                i = i + 1;
                m = 2 * i + 3;
            }

            res.Add(2);
            s.RemoveAll(item => item == 0);
            res.AddRange(s);
        }

        public static double getPeriodTime()
        {
            string runTimeS = Environment.GetEnvironmentVariable("RUN_TIME");
            if (runTimeS == null || runTimeS.Length == 0)
            {
                throw new ArgumentException("Environment RUN_TIME is not set");
            }
            return Convert.ToDouble(runTimeS);
        }

        public static void Main(string[] args)
        {
            DateTime startTime = DateTime.Now;
            double periodTime = getPeriodTime();

            while ((DateTime.Now - startTime).TotalSeconds < periodTime) {
                List<int> res = new List<int>();
                get_primes7(10000000, res);
                Console.Write("Found {0} prime numbers.\n", res.Count);
            }
        }
    }
}