using System;

using Newtonsoft.Json;

public class Program

{

    public void Main()

    {

    var root = new Root();

    var middle = new Middle(1);

    var child = new Child();

    root.Middle = middle;

    middle.Root = root;

    middle.Child = child;

    child.Middle = middle;

    var json = JsonConvert.SerializeObject(root, new JsonSerializerSettings

    {

        Formatting = Newtonsoft.Json.Formatting.Indented,

        ReferenceLoopHandling = ReferenceLoopHandling.Ignore,

        PreserveReferencesHandling = PreserveReferencesHandling.All,        

        TypeNameHandling = TypeNameHandling.All,

    });

    Console.WriteLine(json);

    var deserialized = JsonConvert.DeserializeObject<Root>(json, new JsonSerializerSettings

    {

        PreserveReferencesHandling = PreserveReferencesHandling.All

    });

    Console.WriteLine("Child.Middle == null? " + (deserialized.Middle.Child.Middle == null));

    }

​

    public class Root

    {

        public Root(){Console.WriteLine("Root");}

        public Middle Middle {get;set;}

    }

    public class Middle

    {

        public Middle(){Console.WriteLine("MiddleDefault");}

        //Comment out this attribute to see correct functioning.

        //[JsonConstructor]

        public Middle(int Foo){Console.WriteLine("Middle");}

        public Root Root {get;set;}

        public Child Child {get;set;}

    }

    public class Child

    {

        public Child(){Console.WriteLine("Child");}

        public Middle Middle {get;set;}

    }

}