using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

using System.Threading;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/65764325/how-to-serialize-generic-interface-with-json-net

​

    public interface IInterface<out M>

    {

        M Message { get; }

        string Str { get; }

    }

​

    public class Implementation<M> : IInterface<M>

    {

        public M Message;

        public string Str;

​

        public Implementation(M message, string str)

        {

            Message = message;

            Str = str;

        }

​

        M IInterface<M>.Message => this.Message;

        string IInterface<M>.Str => this.Str;

    }

    public class Sample

    {

        public int X;

    }

​

    public class MyConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType) =>

           objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(IInterface<>);

​

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

        {

            if (!CanConvert(objectType)) // For safety.

                throw new ArgumentException(string.Format("Invalid type {0}", objectType));

            var concreteType = typeof(Implementation<>).MakeGenericType(objectType.GetGenericArguments());

            return serializer.Deserialize(reader, concreteType);

        }

​

        public override bool CanWrite => false;

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) => throw new NotImplementedException();

    }

​

    class TestClass

    {

        public static void Test()

        {

            var js_object_string = @"{ ""Message"" : { ""X"": 100 }, Str : ""abc"" }";

            // Set up Json.NET's global default settings to include MyConverter

            JsonConvert.DefaultSettings = () => new JsonSerializerSettings

                {

                    Converters = { new MyConverter() },

                };

            // And then later, deserialize to IInterface<Sample> via a call that cannot be changed AT ALL:

            var root = JsonConvert.DeserializeObject<IInterface<Sample>>(js_object_string);

            Console.WriteLine("Deserialized {0}:", "IInterface<Sample>");

            root.Dump();

            var json2 = JsonConvert.SerializeObject(root);

            Console.WriteLine("Re-serialized {0}:", "IInterface<Sample>");

            Console.WriteLine(json2);

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(js_object_string), JToken.Parse(json2)));

            Assert.AreEqual(100, root.Message.X);

            Assert.AreEqual("abc", root.Str);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Assembly.GetName().Name,  typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​