using System;

using System.Collections.Generic;

using System.Linq;

using System.Reflection;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        ParseAndDump("First run", @"{

            ""field1"": ""my field 1"",

            ""nested"": {

                ""num"": null,

                ""str"": ""blah"",

                ""dec"": 3.14

            }

        }");

        ParseAndDump("Second run", @"{

            ""field1"": ""new field value""

        }");

        ParseAndDump("Third run", @"{

            ""nested"": null

        }");

    }

    private static void ParseAndDump(string comment, string json)

    {

        Console.WriteLine("--- " + comment + " ---");

        JsonSerializerSettings settings = new JsonSerializerSettings();

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

        FooDTO foo = JsonConvert.DeserializeObject<FooDTO>(json, settings);

        Dump(foo, "");

        Console.WriteLine();

    }

    private static void Dump(IHasFieldStatus dto, string indent)

    {

        foreach (PropertyInfo prop in dto.GetType().GetProperties())

        {

            if (prop.Name == "FieldStatus") continue;

            Console.Write(indent + prop.Name + ": ");

            object val = prop.GetValue(dto);

            if (val is IHasFieldStatus)

            {

                Console.WriteLine();

                Dump((IHasFieldStatus)val, "  ");

            }

            else

            {

                FieldDeserializationStatus status = dto.FieldStatus[prop.Name];

                if (val != null) 

                    Console.Write(val.ToString() + " ");

                if (status != FieldDeserializationStatus.HasValue)

                    Console.Write("(" + status + ")");

                Console.WriteLine();

            }

        }

    }   

}

​

class DtoConverter : JsonConverter

{

    public override bool CanConvert(Type objectType)

    {

        return (objectType.IsClass && 

                objectType.GetInterfaces().Any(i => i == typeof(IHasFieldStatus)));

    }

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

    {

        var jsonObj = JObject.Load(reader);

        var targetObj = (IHasFieldStatus)Activator.CreateInstance(objectType);

        var dict = new Dictionary<string, FieldDeserializationStatus>();

        targetObj.FieldStatus = dict;

        foreach (PropertyInfo prop in objectType.GetProperties())

        {

            if (prop.CanWrite && prop.Name != "FieldStatus")

            {

                JToken value;

                if (jsonObj.TryGetValue(prop.Name, StringComparison.OrdinalIgnoreCase, out value))

                {

                    if (value.Type == JTokenType.Null)

                    {

                        dict.Add(prop.Name, FieldDeserializationStatus.WasSetToNull);

                    }

                    else

                    {

                        prop.SetValue(targetObj, value.ToObject(prop.PropertyType, serializer));

                        dict.Add(prop.Name, FieldDeserializationStatus.HasValue);

                    }

                }

                else

                {

                    dict.Add(prop.Name, FieldDeserializationStatus.WasNotPresent);

                }

            }

        }

        return targetObj;

    }

    public override bool CanWrite

    {

        get { return false; }

    }

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

    {

        throw new NotImplementedException();

    }

}

​

enum FieldDeserializationStatus { WasNotPresent, WasSetToNull, HasValue }

​

interface IHasFieldStatus

{

    Dictionary<string, FieldDeserializationStatus> FieldStatus { get; set; }

}

​

class FooDTO : IHasFieldStatus

{

    public string Field1 { get; set; }

    public BarDTO Nested { get; set; }

    public Dictionary<string, FieldDeserializationStatus> FieldStatus { get; set; }

}

​

class BarDTO : IHasFieldStatus

{

    public int Num { get; set; }

    public string Str { get; set; }

    public bool Bool { get; set; }

    public decimal Dec { get; set; }

    public Dictionary<string, FieldDeserializationStatus> FieldStatus { get; set; }

}

​