Esempio di singleton [C#]

using System;
public class Singleton
{
   private static Singleton istanza;
   private Singleton() {}
   public static Singleton Instance
   {
      get
      {
         if (instanza == null)
         {
            istanza = new Singleton();
         }
         return istanza;
      }
   }
    public void helloWorld()
    {
        Console.WriteLine("Hello World");
    }
}
public class usaSingleton
{
    public static void Main()
    {
        Singleton.Instance.helloWorld();
    }
}