using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        var converter = new CustomIObjectConverter();

        string json = @"{ ""Name"": ""Type A"", ""ID"": 1234 }";

        IObject obj = JsonConvert.DeserializeObject<IObject>(json, converter);

        obj.Dump();

        Console.WriteLine();

        json = @"{ ""Name"": ""Type B"", ""ID"": ""03dd23e4-1c5d-45a8-9366-b8d97a35c93d"" }";

        obj = JsonConvert.DeserializeObject<IObject>(json, converter);

        obj.Dump();

    }

}

​

​

class CustomIObjectConverter : JsonConverter

{

    public override bool CanConvert(Type objectType)

    {

        return typeof(IObject).IsAssignableFrom(objectType);

    }

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

    {

        JObject jo = JObject.Load(reader);

        IObject target;

        if (jo["ID"].Type == JTokenType.Integer)

        {

            target = Activator.CreateInstance<A>();

        }

        else  // Guid

        {

            target = Activator.CreateInstance<B>();

        }

        serializer.Populate(jo.CreateReader(), target);

        return target;

    }

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

    {

        throw new NotImplementedException();

    }

}

​

​

interface IObject

{

    string Name { get; set; }

}

​

class A : IObject

{

    public string Name { get; set; }

    public int ID { get; set; }

}

​

class B : IObject

{

    public string Name { get; set; }

    public Guid ID { get; set; }

}

​