using System;

using System.Collections.Generic;

using System.Diagnostics;

​

public class Program

{

    public static void Main()

    {

        var stopwatch = new Stopwatch();

        stopwatch.Start();

        var generator = new PrimeRobutslyGenerator();

        generator.Generate(int.MaxValue);  

        Console.WriteLine("Position 100 {0}",generator.PrimeNumbers[99]);

        Console.WriteLine("Time : {0}", stopwatch.Elapsed);

        Console.WriteLine("Position 200 {0}",generator.PrimeNumbers[199]);

        Console.WriteLine("Position 500 {0}",generator.PrimeNumbers[499]);

        Console.WriteLine("Position 1000 {0} ",generator.PrimeNumbers[999]);

        Console.WriteLine("Position 1500 {0} ",generator.PrimeNumbers[1499]);       

        Console.WriteLine("Position 2000 {0}",generator.PrimeNumbers[1999]);

        Console.WriteLine("Position 2209 {0}",generator.PrimeNumbers[2208]);

    }

​

    public class PrimeRobutslyGenerator

    {

        public List<double> PrimeNumbers = new List<double>();

        private int MaxPlaces = 0;

        private double MaxNumber = 0;

        public void Generate(double maxNumber)

        {

            MaxNumber = maxNumber;

            MaxPlaces = (int)Math.Floor(Math.Log10(maxNumber)) + 1;

            PrimeNumbers.AddRange(new List<double> { 2, 3, 5, 7 });

            BuildPrimes(3);

            BuildPrimes(7);

            PrimeNumbers.Sort();

        }

        private void BuildPrimes(double number)

        {

            var places = Math.Floor(Math.Log10(number)) + 1;

            if (places == MaxPlaces)

            {

                return;

            }

            for (var i = 1; i <= 9; i++)

            {

                var addition = (Math.Pow(10, places) * i);

                var output = addition + number;

                if (output > MaxNumber)

                {

                    return;

                }

                if (IsPrimeNumber(output))

                {

                    PrimeNumbers.Add(output);

                    BuildPrimes(output);

                }

            }

        }

​

        public bool IsPrimeNumber(double number)

        {

            if (number < 2 || number % 2 == 0)

            {

                return false;

            }

            if (number == 2)

            {

                return true;

            }

​

            var dividOn = (int)Math.Floor(Math.Sqrt(number));

​

            for (var j = 3; j <= dividOn; j += 2)

            {

                if (number % j == 0)

                {

                    return false;

                }

            }

            return true;

        }

    }

}