using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Singleton s1 = Singleton.Instance;

        Singleton s2 = Singleton.Instance;

        if(s1 == s2)

        {

            Console.WriteLine("Hello World");

        }

    }

}

​

​

public sealed class Singleton

{

​

    private static Singleton ins = null;

    private static readonly object padlock = new object();

    Singleton()

    {

    }

    public static Singleton Instance

    {

        get{

            lock (padlock)

            {

                if(ins == null)

                {

                    ins = new Singleton();

                }

                return ins;

            }

        }

    }

}