using System;

using System.Threading;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("--- started ---");

        /*initialization is thread safe*/

        MyClass.MyClassInstance.Value.SomeFunction();

        MyClass.MyClassInstance.Value.SomeFunction();

        MyClass.MyClassInstance.Value.SomeFunction();

        //first batch with no locking

        /*After initilization , function calls are not thread safe. Response from below 3 tasks WILL NOT guarantee 1,2 and 3 response.*/

        Task task1 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetVal(1);});

        Task task2 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetVal(2);});

        Task task3 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetVal(3);});

        //second batch with locking

        /*The object needs to be locked, to be thread safe. Response from below 3 tasks WILL guarantee 1,2 and 3 response.*/

        Task task4 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetValWithLock(1);});

        Task task5 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetValWithLock(2);});

        Task task6 = Task.Factory.StartNew(()=>{MyClass.MyClassInstance.Value.SetValWithLock(3);});

    }

    public class MyClass{

        public static Lazy<MyClass> MyClassInstance = new Lazy<MyClass>(()=> new MyClass());

        public int val1 {get;set;}

        public int val2 {get;set;}

        private MyClass(){

            Console.WriteLine("instance created");

        }

        public void SomeFunction(){

            Console.WriteLine("inside some function");

        }

        public void SetVal(int i){

            val1 = i;

            Console.WriteLine(val1);

        }

        public void SetValWithLock(int i){

            lock(MyClassInstance.Value)

            {

                val2 = i;

                Console.WriteLine(val2);

            }

        }

    }

}