using System;

​

class Singleton

{

    protected Singleton() { }

    private static Singleton _singleton;

​

    public static Singleton Instance 

    {

        get { 

            if (_singleton == null)

            {

                _singleton = new Singleton();

            }

            return _singleton;

        }

    }       

​

    public int CodigoSingleton { get; set; }

}

​

public class Program

{

    public static void Main()

    {

        Singleton singleton0 = Singleton.Instance;

        Singleton singleton1 = Singleton.Instance; // mesma instância de singleton0

        singleton0.CodigoSingleton = 5;

        System.Console.WriteLine(singleton1.CodigoSingleton);

    }

}