Martin Kulov's Blog: Singleton pattern using MemoryBarrier

Singleton pattern using MemoryBarrier

After reading some articles on .NET memory model I understood two things. First you should never rely on MSDN for good multithreading advice. And second – the best way to create a singleton is the following:


public sealed class Singleton 
{
  private Singleton() 
  {
  }
  
  private static Singleton value;
  private static object syncRoot = new Object();
    
  public static Singleton Value 
  {
    get 
    {
      if (Singleton.value == null) 
      {
        lock (syncRoot) 
        {
          if (Singleton.value == null) 
          {
            Singleton newVal = new Singleton();
    
            // Insure all writes used 
            // to construct new value have been flushed. 
            System.Threading.Thread.MemoryBarrier(); 

            // publish the new value 
            Singleton.value = newVal;         
          }
        }
      }
    
      return Singleton.value;
    }
  }      
}