using System;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        //var a = Singleton.Getinstance;

        //Singleton.DerivedSingleton ds = new Singleton.DerivedSingleton();

        //ds.Method1();

        //a.Method1("from main");

        Parallel.Invoke(

        ()=> printfrom1(), ()=> printfrom2()

        );

    }

    public static void printfrom1()

        {

        //Console.WriteLine("2");

        var a = Singleton.Getinstance;

        a.Method1("from 1");

        }

    public static void printfrom2()

        {;

        var b = Singleton.Getinstance;

        b.Method1("from 2");

        }

}

​

public sealed class Singleton

{

    private static readonly object instanceLock = new object();

    public static int counter = 0;

    private Singleton()

    {

    counter++;

    Console.WriteLine("counter value {0}", counter);

    }

​

private static Singleton instance = null;

    public static Singleton Getinstance

    {

        get

        {

        lock(instanceLock)

        {

                if (instance == null)

                    instance = new Singleton();

                    return instance;

                }

        }

    }

​

public void Method1(string x)

{

Console.WriteLine(x);

}

//public class DerivedSingleton: Singleton

//{

​

//}

}

​

​

​

​