using System;
using System.Diagnostics;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            var sw = Stopwatch.StartNew();

            for (int i = 0; i < 10000000; i++)
            {
                var instance = LazySingleton.Instance;
                //var instance = DoubleCheckLockSingleton.Instance;
            }
            Console.WriteLine(sw.ElapsedMilliseconds);
        }
    }

    public class LazySingleton
    {
       private static readonly Lazy<LazySingleton> _instance
           = new Lazy<LazySingleton>(() => new LazySingleton(), isThreadSafe: true);

       private LazySingleton() {}

       public static LazySingleton Instance => _instance.Value;
    }

    public class DoubleCheckLockSingleton
    {
        private static readonly object SyncObj = new object();
        private static volatile DoubleCheckLockSingleton _instance = null;

        private DoubleCheckLockSingleton(){ }

        public static DoubleCheckLockSingleton Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (SyncObj)
                    {
                        if (_instance == null)
                        {
                            _instance = new DoubleCheckLockSingleton();
                        }
                    }
                }
                return _instance;
            }
        }
    }
}