Thread Safety in Singleton Design Pattern using Lazy keyword

 # Thread Safety in Singleton Design Pattern using Lazy keyword

Lazy keyword provides support for lazy initialization. In order to make a property as lazy, we need to pass the type of object to the lazy keyword which is being lazily initialized.

By default, Lazy<T> objects are thread-safe. In multi-threaded scenarios, the first thread which tries to access the Value property of the lazy object will take care of thread safety when multiple threads are trying to access the Get Instance at the same time.

Therefore, it does not matter which thread initializes the object or if there are any thread race conditions that are trying to access this property.

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace SingletonDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            Parallel.Invoke(
                () => PrintStudentDetails(),
                () => PrintEmployeeDetails()
            );
            Console.ReadLine();
        }

        private static void PrintEmployeeDetails()
        {
            Singleton fromEmployee = Singleton.GetInstance;
            fromEmployee.PrintDetails("From Employee");
        }

        private static void PrintStudentDetails()
        {  
            Singleton fromStudent = Singleton.GetInstance;
            fromStudent.PrintDetails("From Student");
        }
    }
}

Singleton.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace SingletonDemo
{
   
    public sealed class Singleton
    {
        private static int counter = 0;
       
        private Singleton()
        {
            counter++;
            Console.WriteLine("Counter Value " + counter.ToString());
        }
        private static readonly Lazy<Singleton> instance =
new Lazy<Singleton>(()=>new Singleton());
       
        public static Singleton GetInstance
        {
            get
            {
                return instance.Value;
            }
        }
       
        public void PrintDetails(string message)
        {
            Console.WriteLine(message);
        }       
    }
}