C# Advent Calendar 2015-12-25 #5

CSharp-Advent-Calendar-2015-12-25-5.cs

using System;
using System.Linq;
using System.Security.Cryptography;
using System.Threading;

namespace ConsoleApplication5
{
    static class BetterRandom
    {
        [ThreadStatic]
        static Random Random;

        public static Random GetRandom()
        {
            if (Random == null)
            {
                using (var provider = new RNGCryptoServiceProvider())
                {

                    var bytes = new byte[8];

                    provider.GetBytes(bytes);

                    var seed = BitConverter.ToInt32(bytes, 0);

                    Random = new Random(seed);
                }
            }

            return Random;
        }
    }

    static class Program
    {
        static void Main(string[] args)
        {
            const int count = 1000 * 1000;

            var values = new int[count];

            int done = 0;

            for (var i = 0; i < count; i++)
            {
                ThreadPool.QueueUserWorkItem(state =>
                {
                    var random = BetterRandom.GetRandom();

                    var index = (int)state;

                    values[index] = random.Next();

                    Interlocked.Add(ref done, 1);
                }, i);
            }

            while (done < count)
            {
                Thread.Sleep(0);
            }

            var zero = values.Where(value => value == 0).Count();
            Console.WriteLine(zero);
        }
    }
}