using System;

using Newtonsoft.Json;

using System.ComponentModel;

public class Program

{

    public static void Main()

    {

        //var myClass = new MyClasss();

        //var myObj = new Obj();

        //myObj.x="";

        //myObj.y="test str";

        //myClass.myStr = "Hi";

        //myClass.obj= myObj;

        string json = @"{obj: { x: '', y: 'test str' }, myStr: 'Hi'}";

        MyClasss myClass = JsonConvert.DeserializeObject<MyClasss>(json);

​

        var settings = new JsonSerializerSettings();

        settings.NullValueHandling = NullValueHandling.Ignore;

        settings.DefaultValueHandling = DefaultValueHandling.Ignore;

        Console.WriteLine(JsonConvert.SerializeObject(myClass, settings));

    }

}

​

    public class Obj    {

        [DefaultValue("")]

        public string x { get; set; } 

        [DefaultValue("")]

        public string y { get; set; } 

​

    }

​

    public class MyClasss    {

        public Obj obj { get; set; } 

        [DefaultValue("")]

        public string myStr { get; set; } 

​

    }