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.Diagnostics;

​

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/65899532/best-way-to-upgrade-json-field-to-a-class-structure

​

    public class Author

    {

        public string name;

        public string email;

        public string url;

    }

​

    public class AuthorConverter : JsonConverter

    {

        public override bool CanConvert(Type objectType) { return objectType == typeof(Author); }

​

        public override bool CanWrite { get { return false; } }

​

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

        {

            throw new NotImplementedException();

        }

​

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

        {

            try

            {

                if (reader.MoveToContentAndAssert().TokenType == JsonToken.Null)

                    return null; // Or throw an exception if you don't want to allow null.

                else if (reader.TokenType == JsonToken.String)

                    return new Author { name = (string) reader.Value };

                else

                {

                    var author = new Author();

                    serializer.Populate(reader, author);

                    return author;

                }           

            }

            catch (Exception ex)

            {

                UnityEngine.Debug.Log(ex);

                throw;

            }

        }

    }

​

    public static partial class JsonExtensions

    {

        // Skip past any comments to the next content token, asserting that the file was not truncated.

        public static JsonReader MoveToContentAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (reader.TokenType == JsonToken.None)       // Skip past beginning of stream.

                reader.ReadAndAssert();

            while (reader.TokenType == JsonToken.Comment) // Skip past comments.

                reader.ReadAndAssert();

            return reader;

        }

​

        // Read (advance to) the next token, asserting that the file was not truncated.

        public static JsonReader ReadAndAssert(this JsonReader reader)

        {

            if (reader == null)

                throw new ArgumentNullException();

            if (!reader.Read())

                throw new JsonReaderException("Unexpected end of JSON stream.");

            return reader;

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var settings = new JsonSerializerSettings

            {

                Converters = { new AuthorConverter() },

            };

            var json1in = "\"my name\"";

            var author1 = JsonConvert.DeserializeObject<Author>(json1in, settings);

            Assert.IsTrue(author1.name == "my name");

            var json1 = JsonConvert.SerializeObject(author1, settings);

            Console.WriteLine(json1);

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(json1), JToken.Parse(@"{""name"":""my name"",""email"":null,""url"":null}")));

            var json2in = @"{""name"":""my name"",""email"":""my email"",""url"":""my url""}";

            var author2 = JsonConvert.DeserializeObject<Author>(json2in, settings);

            Assert.IsTrue(author2.name == "my name" && author2.email == "my email" && author2.url == "my url");

​

            var json2 = JsonConvert.SerializeObject(author2, settings);

​

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(json2), JToken.Parse(json2in)));

        }   

    }

​

    // Mockup for dotnetfiddle

    namespace UnityEngine

    {

        public static class Debug

        {

            public static void Log(object s)

            {

                Console.WriteLine(s);

            }

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​