using System;

using System.IO;

using System.Text;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

​

public class Program

{

    public static void Main()

    {

        var ser = GetSerializer();

        var sb = new StringBuilder();

        var subject = QuestionAnswer.Yes;

        using(var text = new StringWriter(sb))

        {

            ser.Serialize(text, subject);

        }

        Console.WriteLine(sb.ToString());

    }

    public static JsonSerializer GetSerializer()

    {

        var settings = new JsonSerializerSettings();

        settings.Converters.Add(new StringEnumConverter());

        return JsonSerializer.Create(settings);

    }

}

​

public enum QuestionAnswer

{

    NA,

    No,

    Yes

}