using System;

using System.ComponentModel;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("--- test #1 ---");

        var obj = new ParentSample();

        Console.WriteLine(JsonHelper.SerializeToMinimalJson(obj));

        Console.WriteLine("--- test #2 ---");

        obj = new ParentSample();

        obj.Sample.Value = 1;

        obj.Sample.Name = "blah";

        Console.WriteLine(JsonHelper.SerializeToMinimalJson(obj));

        Console.WriteLine("--- test #3 ---");

        obj = new ParentSample();

        obj.Sample.Value = 3;

        obj.Sample.Name = "foo";

        Console.WriteLine(JsonHelper.SerializeToMinimalJson(obj));

    }

}

​

public class ParentSample 

{

    public Sample Sample { get; private set; }

    public ParentSample() 

    {

        Sample = new Sample();

    }

}

​

public class Sample 

{

    [DefaultValue(3)]

    public int Value { get; set; }

    [DefaultValue("foo")]

    public string Name { get; set; }

}

​

​

​

public static class JsonHelper

{

    public static string SerializeToMinimalJson(object obj)

    {

        var serializer = new JsonSerializer();

        serializer.NullValueHandling = NullValueHandling.Ignore;

        serializer.DefaultValueHandling = DefaultValueHandling.Ignore;

        return JToken.FromObject(obj, serializer).RemoveEmptyChildren().ToString();

    }

    public static JToken RemoveEmptyChildren(this JToken token)

    {

        if (token.Type == JTokenType.Object)

        {

            JObject copy = new JObject();

            foreach (JProperty prop in token.Children<JProperty>())

            {

                JToken child = prop.Value;

                if (child.HasValues)

                {

                    child = child.RemoveEmptyChildren();

                }

                if (!child.IsEmptyOrDefault())

                {

                    copy.Add(prop.Name, child);

                }

            }

            return copy;

        }

        else if (token.Type == JTokenType.Array)

        {

            JArray copy = new JArray();

            foreach (JToken item in token.Children())

            {

                JToken child = item;

                if (child.HasValues)

                {

                    child = child.RemoveEmptyChildren();

                }

                if (!child.IsEmptyOrDefault())

                {

                    copy.Add(child);

                }

            }

            return copy;

        }

        return token;

    }

​

    public static bool IsEmptyOrDefault(this JToken token)

    {

        return (token.Type == JTokenType.Array && !token.HasValues) ||

               (token.Type == JTokenType.Object && !token.HasValues);

    }

​

}