using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

public class Program

{

    public static void Main()

    {

        Bar bar = new Bar

        {

            Foo = Foo.Two,

            Fah = Fah.Gamma,

            Fizz = Fizz.Bang

        };

        JsonSerializerSettings settings = new JsonSerializerSettings();

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

        settings.Formatting = Formatting.Indented;

        string json = JsonConvert.SerializeObject(bar, settings);

        Console.WriteLine(json);

    }

}

​

enum Foo { One = 1, Two = 2, Three = 3 }

enum Fah { Alpha = 1, Beta = 2, Gamma = 3, Delta = 4 }

enum Fizz { Bang = 1, Pop = 2, Pow = 3 }

​

class Bar

{

    public Foo Foo { get; set; }

    public Fah Fah { get; set; }

    public Fizz Fizz { get; set; }

}

​

class StringEnumExceptFooConverter : StringEnumConverter

{

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

    {

        if (value is Foo || value is Foo?)

        {

            writer.WriteValue(value);

        }

        else

        {

            base.WriteJson(writer, value, serializer);

        }

    }

}

​