using System;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

​

public class Program

{

    public static void Main()

    {

        var employee = new Employee

        {

            FirstName = "FirstName",

            LastName = "LastName",

            Roles = new List<string>

            {

                "Admin"

            }

        };

        string json = JsonConvert.SerializeObject(employee, Formatting.Indented, new JsonSerializerSettings

        {

            Converters = new List<JsonConverter> { new EvalResultConverter() },

            Error = (_, args) => args.ErrorContext.Handled = true,

            ReferenceLoopHandling = ReferenceLoopHandling.Ignore

        });

​

        Console.WriteLine(json);

    }

}

​

public class EvalResultConverter : JsonConverter

{

    public override bool CanRead => false;

    public override bool CanWrite => true;

​

    public override bool CanConvert(Type objectType) => true;

​

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

        => throw new NotImplementedException();

​

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

    {

        var token = JToken.FromObject(value!);

        if (token.Type is JTokenType.Object)

        {

            var tokenObject = (JObject)token;

            foreach (var property in tokenObject.Properties())

            {

                if (property.Value.Type is JTokenType.Object && typeof(Optional).IsAssignableFrom(value!.GetType().GetProperty(property.Name)!.PropertyType))

                {

                    var propertyObject = (JObject)property.Value;

                    tokenObject[property.Name] = propertyObject["HasValue"]!.Value<bool>() ? propertyObject["Value"] : null;

                }

            }

            tokenObject.WriteTo(writer);

        }

        else token.WriteTo(writer);

    }

}

​

public class Optional

{

    public bool HasValue { get; set; }

    public object Value { get; set; }

}

​

​

public class Employee

{

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public IList<string> Roles { get; set; }

    public Optional HasMiddleName = new Optional

    {

        HasValue = false

    };

    public Optional HasLastName = new Optional

    {

        HasValue = true,

        Value = "LastName"

    };

    public Optional HasFirstName = new Optional

    {

        HasValue = true,

        Value = "FirstName"

    };

    public Optional HasAcronym = new Optional

    {

        HasValue = false

    };

}