StructWrapper.cs

using System;
using System.Linq;
using Newtonsoft.Json;

namespace XXX
{
    [JsonConverter(typeof(StructWrapperConverter))]
    public sealed class StructWrapper<T> where T : struct
    {
        public T Value { get; }

        public StructWrapper(T value)
        {
            Value = value;
        }
    }

    public class StructWrapperConverter : JsonConverter
    {
        public override bool CanConvert(Type objectType) =>
            objectType.IsGenericType && objectType.GetGenericTypeDefinition() == typeof(StructWrapper<>);

        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
        {
            Type type = value!.GetType();
            var prop = type.GetProperties().Single();
            var propVal = prop.GetValue(value, null);
            serializer.Serialize(writer, propVal);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object? existingValue,
            JsonSerializer serializer)
        {
            var argType = objectType.GetGenericArguments().Single();
            return serializer.Deserialize(reader, argType)!;
        }

        public override bool CanRead => true;
    }
}