using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using System;

using System.Collections;

using System.Collections.Generic;

​

namespace JsonConverterTest

{

    class Program

    {

        static void Main(string[] args)

        {

            var s1 = @"

{

  ""data"": {

    ""items"": [

       {

          ""id"": 1

       },

       {

          ""id"": 2

       }

    ]

  }

}";

            var s2= @"

{

  ""data"": {

    ""id"": 1

  }

}";

​

            var t1 = JsonConvert.DeserializeObject<Response<Simple>>(s1);

            var t2 = JsonConvert.DeserializeObject<Response<Simple>>(s2);

            t1.Dump();

            t2.Dump();

        }

    }

​

    public class Simple

    {

        [JsonProperty("id")]

        public int Id { get; set; }

    }

​

    public class Response<T>

    {

        [JsonProperty("version")]

        public string Version { get; set; }

​

        [JsonConverter(typeof(SingleOrArrayConverter))]

        public List<T> Data { get; set; }

​

        [JsonProperty("_links")]

        public Links Links { get; set; }

    }

​

    public class Links

    { 

    }

​

    public class SingleOrArrayConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType)

        {

            throw new NotImplementedException();

        }

​

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

        {

            JToken token = JToken.Load(reader);

            if (token["items"]?.Type == JTokenType.Array)

            {

                return token["items"].ToObject(objectType);

            }

            var genericType = objectType.GenericTypeArguments[0];

            var listType = typeof(List<>);

            var constructedListType = listType.MakeGenericType(genericType);

            var instance = (IList)(Activator.CreateInstance(constructedListType));

            instance.Add(token.ToObject(genericType));

            return instance;

        }

​

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

        {

            throw new NotImplementedException();

        }

    }

}

​