using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Serialization;

public class Program

{

    public static void Main()

    {

        JsonSerializerSettings settings = new JsonSerializerSettings();

        // Comment out the following line and CanConvert never gets called on FooConverter for any type

        // yet the FooConverter is still working due to the JsonConverter attribute applied to Wrapper.Foo

        settings.Converters.Add(new FooConverter());

        settings.Converters.Add(new BarConverter());

        settings.Formatting = Formatting.Indented;

        Wrapper w = new Wrapper

        {

            Foo = new Foo

            {

                A = "bada",

                B = "boom",

            },

            Bar = new Bar

            {

                C = "bada",

                D = "bing"

            }

        };

        string json = JsonConvert.SerializeObject(w, settings);

        Console.WriteLine(json);

    }

    class Wrapper

    {

        // Comment out this attribute and CanConvert will be called on FooConverter for type Foo

        // due to the fact that the FooConverter has been added to the JsonSerializerSettings

        [JsonConverter(typeof(FooConverter))]

        public Foo Foo { get; set; }

        public Bar Bar { get; set; }

    }

    class Foo

    {

        public string A { get; set; }

        public string B { get; set; }

    }

    class Bar

    {

        public string C { get; set; }

        public string D { get; set; }

    }

    class FooConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType)

        {

            bool result = typeof(Foo).IsAssignableFrom(objectType);

            Console.WriteLine("FooConverter CanConvert() called for type " + objectType.Name + " (result = " + result + ")");

            return result;

        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            var foo = (Foo) value;

            JObject jo = new JObject();

            jo.Add("AplusB", new JValue(foo.A + " " + foo.B));

            jo.WriteTo(writer);

        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

    class BarConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType)

        {

            bool result = typeof(Bar).IsAssignableFrom(objectType);

            Console.WriteLine("BarConverter CanConvert() called for type " + objectType.Name + " (result = " + result + ")");

            return result;

        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            var bar = (Bar) value;

            JObject jo = new JObject();

            jo.Add("CplusD", new JValue(bar.C + " " + bar.D));

            jo.WriteTo(writer);

        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

}