class Program
    {
        static void Main(string[] args)
        {
           Debug.Print( (bar._foo == null) + "\n");
           Debug.Print( (foo._bar == null).ToString());
            int i = 34;
        }

        static readonly Bar bar = new Bar(foo);
        static readonly Foo foo = new Foo(bar);
    }

    class Bar
    {
        public readonly Foo _foo;

        public Bar(Foo foo)
        {
            _foo = foo;
        }
    }

    class Foo
    {
        public readonly Bar _bar;

        public Foo(Bar bar)
        {
            _bar = bar;
        }
    }

class Parent
    {
        Child children[];
    }

class Child
    {
        Parent parent;
    }