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 Newtonsoft.Json.Linq;

​

using System.Text.Json;

using System.Text.Json.Serialization;

​

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

​

//https://stackoverflow.com/questions/67028864/jsonconstuctorattribute-in-system-text-json-results-in-exception-but-not-with-n

​

    [JsonConverter(typeof(AvatarConverter))]

    public class AvatarImage

    {

        public Byte[] Data { get; set; } = null;

    }

​

    class AvatarConverter : JsonConverter<AvatarImage>

    {

        class AvatarDTO { public string Data { get; set; } }

        public override AvatarImage Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

        {

            var dto = JsonSerializer.Deserialize<AvatarDTO>(ref reader, options);

            var index = dto.Data?.IndexOf(',') ?? -1;

            return new AvatarImage { Data = dto.Data == null ? null : Convert.FromBase64String(index < 0 ? dto.Data : dto.Data.Remove(0, index + 1)) };

        }

​

        public override void Write(Utf8JsonWriter writer, AvatarImage value, JsonSerializerOptions options) =>

            JsonSerializer.Serialize(writer, new { Data = value.Data }, options);

    }

​

    class TestClass

    {

        public static void Test()

        {

            var avatar1 = new AvatarImage

            {

                Data = Enumerable.Repeat((byte)1, 10).ToArray(),

            };

            var json1 = JsonSerializer.Serialize(avatar1);

​

            Console.WriteLine(json1);

            var token = JToken.Parse(json1);

            token["Data"] = "header,"+(string)token["Data"];

            var json11 = token.ToString(Newtonsoft.Json.Formatting.None);

            Console.WriteLine(json11);

            var avatar2 = JsonSerializer.Deserialize<AvatarImage>(json11);

            var json2 = JsonSerializer.Serialize(avatar2);

            Console.WriteLine(json2);

​

            Assert.IsTrue(Enumerable.SequenceEqual(avatar1.Data, avatar2.Data));

            Assert.AreEqual(json1, json2);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

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

            Console.WriteLine("System.Text.Json version: " + 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 "";

        }

    }

​