FSharpOptionConverter : JsonConverter

FSharpOptionConverter.cs

public class FSharpOptionConverter : JsonConverter
{
    private static MethodInfo _getInnerValue = typeof (FSharpOptionConverter).GetMethod("GetInnerValue",
                                                                                        BindingFlags.Instance |
                                                                                        BindingFlags.NonPublic);
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        if (value != null)
        {
            var optionValueType = value.GetType().GetGenericArguments().Single();
            var method = _getInnerValue.MakeGenericMethod(new[] {optionValueType});
            var innerValue = method.Invoke(this, new[]{value});
            serializer.Serialize(writer, innerValue);
        }
        else
        {
            serializer.Serialize(writer, null);
        }
    }

    private object GetInnerValue<T>(FSharpOption<T> option)
    {
        if (FSharpOption<T>.get_IsNone(option))
        {
            return null;
        }
        else
        {
            return option.Value;
        }
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var optionValueType = objectType.GetGenericArguments().Single();
        var makeGenericType = typeof (FSharpOption<>).MakeGenericType(new Type[] {optionValueType});
        if (reader.TokenType == JsonToken.Null)
        {
            return MakeNone(makeGenericType);
        }
        var value = serializer.Deserialize(reader, optionValueType);

        if (value == null)
        {
            return MakeNone(makeGenericType);
        }
        else
        {
            var someMethodInfo = makeGenericType.GetMethod("Some", BindingFlags.Static | BindingFlags.Public);
            return someMethodInfo.Invoke(null, new[] {value});
        }
    }

    private static object MakeNone(Type makeGenericType)
    {
        return makeGenericType
            .GetProperty("None")
            .GetGetMethod()
            .Invoke(null, new object[0]);
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(FSharpOption<>);
    }
}