using System;

public class Program

{

    public static event Action EventTrue;

    public static event Action EventFalse;

    static bool foo;

    public static void Main()

    {

        var b = false;

        Subscribe(()=>Invert(ref b));

        EventTrue.Invoke();

        Console.WriteLine(b);

        EventFalse.Invoke();

        Console.WriteLine(b);

    }

    public static void Subscribe(Action a)

    {

        EventTrue += () => a();

        EventFalse += () => a();

    }

    public static void Invert(ref bool b)

    {

    b = !b;

    }

}