Answer to Question #340866 in C# for Babar302

Question

Create C# programs for singleton design pattern using following implementations

1- Thread-Safety Singleton using Double-Check Locking.

2- Thread-safe without a lock.

3- Using .NET 4's Lazy<T> type.

Answer 1

using System;
//lock
public sealed class Singleton
{
   private static volatile Singleton instance;
   private static object syncRoot = new object();

   private Singleton() {}

   public static Singleton Instance
   {
      get 
      {
         if (instance == null) 
         {
            lock (syncRoot) 
            {
               if (instance == null) 
                  instance = new Singleton();
            }
         }

         return instance;
      }
   }
}
//lazy
public sealed class Singleton
{
    private static readonly Lazy<Singleton> lazy
        = new Lazy<Singleton>(() => new Singleton());

    public static Singleton Instance
        => lazy.Value;

    private Singleton() { }
}

//safe to threads
public sealed class Singleton
{
    private static readonly Singleton instance = new Singleton();

    static Singleton()
    {
    }

    private Singleton()
    {
    }

    public static Singleton Instance
    {
        get
        {
            return instance;
        }
    }
}