using System;

using System.Collections.Generic;

​

public interface IGreeter

{

    void Greet();

}

​

public struct Greeter : IGreeter

{

    public int GreetsAmount;

​

    public void Greet()

    {

        GreetsAmount++;

        Console.WriteLine("Hi!");

    }

}

​

public class Test

{

    public static void Main()

    {

        var greeters = new List<IGreeter> { new Greeter(), new Greeter(), new Greeter() };

        GreetAll(greeters);

        var greeter = new Greeter();

        HackGreeter(ref greeter);

        Console.WriteLine(greeter.GreetsAmount);

    }

    public static void GreetAll(List<IGreeter> greeters)

    {

        foreach (var greeter in greeters)

        {

            greeter.Greet();

        }

    }

    public static void HackGreeter(ref Greeter greeter)

    {

        greeter.GreetsAmount = 10;

    }

}