using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            {

              ""Foo"": ""Whatever"",

              ""Bar"": [

                {

                  ""Name"": ""Enrico"",

                  ""Age"": 33,

                  ""Country"": ""Italy""

                },

                {

                  ""Type"": ""Video"",

                  ""Year"": 2004

                },

                {

                  ""Name"": ""Sam"",

                  ""Age"": 18,

                  ""Country"": ""USA""

                },

                {

                  ""Type"": ""Book"",

                  ""Year"": 1980

                }

              ]

            }";

​

        var root = JsonConvert.DeserializeObject<ClassToDeserialize>(json);

        Console.WriteLine("Foo: " + root.Foo);

        foreach (IBar bar in root.Bar)

        {

            Console.Write($"Type: {bar.Type}, ");

            if (bar.Type == "Person")

            {

                Person p = (Person)bar;

                Console.WriteLine($"Name: {p.Name}, Age: {p.Age}, Country: {p.Country}");

            }

            else

            {

                Item i = (Item)bar;

                Console.WriteLine($"Year: {i.Year}");

            }

        }

    }

}

​

[JsonConverter(typeof(BarConverter))]

interface IBar

{

    string Type { get; }

}

​

class Person : IBar

{

    public string Type => "Person";

    public string Name { get; set; }

    public int Age { get; set; }

    public string Country { get; set; }

}

​

class Item : IBar

{

    public string Type { get; set; }

    public int Year { get; set; }

}

​

class ClassToDeserialize

{

    public string Foo { get; set; }

    public List<IBar> Bar { get; set; }

}

​

public class BarConverter : JsonConverter

{

    public override bool CanConvert(Type objectType)

    {

        return typeof(IBar).IsAssignableFrom(objectType);

    }

​

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

    {

        JObject jo = JObject.Load(reader);

​

        // If the "Age" property is present in the JSON, it's a person, otherwise it's an item

​

        IBar bar;

        if (jo["Age"] != null)  // case sensitive

        {

            bar = new Person();

        }

        else

        {

            bar = new Item();

        }

​

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

​

        return bar;

    }

​

    public override bool CanWrite => false;

​

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

    {

        throw new NotImplementedException();

    }

}

​