using System;

namespace SingletonDemo

{

    public sealed class Singleton

    {

        //This variable value will be increment by 1 each time the object of the class is created

        private static int Counter = 0;

        //This variable is going to store the Singleton Instance

        private static Singleton Instance = null;

        //To use the lock, we need to create one variable

        private static readonly object Instancelock = new object();

        //The following Static Method is going to return the Singleton Instance

        public static Singleton GetInstance()

        {

            //This is thread-safe

            //As long as one thread locks the resource, no other thread can access the resource

            //As long as one thread enters into the Critical Section, 

            //no other threads are allowed to enter the critical section

            lock (Instancelock)

            { //Critical Section Start

                if (Instance == null)

                {

                    Instance = new Singleton();

                }

            } //Critical Section End

            //Once the thread releases the lock, the other thread allows entering into the critical section

            //But only one thread is allowed to enter the critical section

            //Return the Singleton Instance

            return Instance;

        }

        private Singleton()

        {

            //Each Time the Constructor is called, increment the Counter value by 1

            Counter++;

            Console.WriteLine("Counter Value " + Counter.ToString());

        }

        //The following method can be accessed from outside of the class by using the Singleton Instance

        public void PrintDetails(string message)

        {

            Console.WriteLine(message);

        }

    }

}