/*

Threadsafe Singleton can be implemented in two approach

1. Using double check lock approach (old way)

2. Using modern Lazy loading

3. lock(lockedObject) //lockedObject cannot be null

*/

​

​

using System;

public class MySingletonWithDoubleCheck {

    private static object myLock = new object();

    private static  MySingletonWithDoubleCheck mySingleton = null; 

​

    private MySingletonWithDoubleCheck() {

    }

​

    public static MySingletonWithDoubleCheck GetInstance() {

        if (mySingleton == null) { // Check first time if Instance is available

            lock (myLock) {

                if (mySingleton == null) { // Need to check again as there is a chance that object would have created between first check and lock

                    mySingleton = new MySingletonWithDoubleCheck();

                }

            }

        }

        return mySingleton;

    }

    public  void PrintTime()

    {

        Console.WriteLine("MySingletonWithDoubleCheck  "+DateTime.Now.ToString());

    }

}

​

​

public class MySingletonWithLazy

{

    private static readonly Lazy<MySingletonWithLazy> _mySingleton = new Lazy<MySingletonWithLazy>(() => new MySingletonWithLazy());

​

    private MySingletonWithLazy() { }

​

    public static MySingletonWithLazy GetInstance()

    {       

            return _mySingleton.Value;        

    }

    public  void PrintTime()

    {

        Console.WriteLine("MySingletonWithLazy  "+DateTime.Now.ToString());

    }

}

​

public class Program

{

    public static void Main(string[] args)

    {

        MySingletonWithDoubleCheck instance = MySingletonWithDoubleCheck.GetInstance();

        instance.PrintTime();

        MySingletonWithLazy instance1 = MySingletonWithLazy.GetInstance();

        instance1.PrintTime();

    }

}