using System;

using System.Threading;

public class Program

{

    public static void Main()

    {

        TwoInstance T1 = new TwoInstance();

        TwoInstance T2 = new TwoInstance();

        TwoInstance T3 = new TwoInstance(); // this will throw an error :) 

    }

    public class TwoInstance

    {

        private static int countInstances=1; 

        //*if you want to get the count outside then make it 

        //public or create a static int method which will return this property*

        public TwoInstance()

        {

            Console.WriteLine("Instance" + countInstances + "Created");

            //  countInstances++;    *this is the basic thing which came 

            //  into my mind at the time of iterview but this is not thread safe*

            Interlocked.Increment(ref countInstances); 

            // thread safe way to increment the counter or we can use LOCK keyword

            if(countInstances>=3)

            {

                throw new Exception("You cannot create more then two object");

            }

        }

         ~TwoInstance()

         {

            Interlocked.Decrement(ref countInstances);

         }

    }

}