gistfile1.cs

using System;
using System.Collections.Generic;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        private static int count;

        static void Main(string[] args)
        {
            IWorker worker1 = new Worker1();
            IWorker worker2 = new Worker2();
            IWorker worker3 = new Worker3();
            count = 100;
            RepeatWorker(worker1);
            RepeatWorker(worker2);
            RepeatWorker(worker3);

            var watch = System.Diagnostics.Stopwatch.StartNew();
            count = 100000000;
            RepeatWorker(worker1);
            watch.Stop();
            Console.WriteLine(watch.ElapsedMilliseconds);
            watch.Restart();
            RepeatWorker(worker2);
            watch.Stop();
            Console.WriteLine(watch.ElapsedMilliseconds);
            watch.Restart();
            RepeatWorker(worker3);
            watch.Stop();
            Console.WriteLine(watch.ElapsedMilliseconds);
        }


        private static void RepeatWorker(IWorker workeer)
        {
            for (int i = 0; i < count; i++)
            {
                workeer.DoWork();
            }
        }
    }

    

    interface IWorker
    {
        void DoWork();
    }

    class Worker1 : IWorker
    {
        private int isRunning = 0;

        public void DoWork()
        {
            if (Interlocked.CompareExchange(ref isRunning, 1, 0) == 0)
            {
            }
        }

    }

    class Worker2: IWorker
    {
        private volatile int isRunning = 0;

        public void DoWork()
        {
            if (isRunning == 0 && Interlocked.CompareExchange(ref isRunning, 1, 0) == 0)
            {
            }
        }

        private void DoTheMagic()
        {
            // do something interesting
        }
    }

    class Worker3 : IWorker
    {

        public void DoWork()
        {
        }

        private void DoTheMagic()
        {
            // do something interesting
        }
    }
}

The result is 777, 411, 343