using System;

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Collections.Generic;

using System.Reflection;

using System.Linq;

public class Program

{

    [JsonOneOf(typeof(ShipmentRefQuery), nameof(ShipmentRefQuery.ShipmentReferenceIds))]

    [JsonOneOf(typeof(FcAllocationRefQuery), nameof(FcAllocationRefQuery.FcAllocationReferenceIds))]

    [JsonOneOf(typeof(LegacyOrderQuery), nameof(LegacyOrderQuery.LegacyOrderIds))]

    public abstract class ShipmentQuery {}

    public class ShipmentRefQuery : ShipmentQuery { public Guid[] ShipmentReferenceIds { get; init; } }

    public class FcAllocationRefQuery : ShipmentQuery { public Guid[] FcAllocationReferenceIds { get; init; } }

    public class LegacyOrderQuery : ShipmentQuery { public int[] LegacyOrderIds { get; init; } }

    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]

    public class JsonOneOfAttribute : Attribute

    {

        public Type DerivedType { get; }

        public string DiscriminatingPropertyName { get; }

​

        public JsonOneOfAttribute(Type derivedType, string discriminatingPropertyName)

        {

            DerivedType = derivedType;

            DiscriminatingPropertyName = discriminatingPropertyName;

        }

    }

​

    public class OneOfJsonConverter<TBase> : JsonConverter<TBase> where TBase : class

    {

        private readonly Dictionary<string, Type> _discriminatorMap;

​

        public OneOfJsonConverter()

        {

            _discriminatorMap = typeof(TBase)

                .GetCustomAttributes<JsonOneOfAttribute>()

                .ToDictionary(attr => attr.DiscriminatingPropertyName, attr => attr.DerivedType);

        }

​

        public override TBase Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

        {

            using var jsonDoc = JsonDocument.ParseValue(ref reader);

            var jsonObject = jsonDoc.RootElement;

​

            foreach (var entry in _discriminatorMap)

            {

                if (jsonObject.TryGetProperty(entry.Key, out _))

                {

                    return (TBase)JsonSerializer.Deserialize(jsonObject, entry.Value, options);

                }

            }

​

            throw new JsonException("Type could not be determined");

        }

​

        public override void Write(Utf8JsonWriter writer, TBase value, JsonSerializerOptions options)

        {

            JsonSerializer.Serialize(writer, value, value.GetType(), options);

        }

    }

    public class OneOfJsonConverterFactory : JsonConverterFactory

    {

        public override bool CanConvert(Type typeToConvert)

        {

            return typeToConvert.GetCustomAttributes<JsonOneOfAttribute>(false).Any();

        }

​

        public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)

        {

            var converterType = typeof(OneOfJsonConverter<>).MakeGenericType(typeToConvert);

            return (JsonConverter)Activator.CreateInstance(converterType);

        }

    }

    public static void Main()

    {

        var options = new JsonSerializerOptions();

        options.Converters.Add(new OneOfJsonConverterFactory());

        var serialized = "{\"FcAllocationReferenceIds\":[\"b840b54f-815a-414c-b446-39ccfaf2ac12\",\"33afae1a-d8c4-410d-b72b-86ed5051c97f\"]}";

        var deserialized = JsonSerializer.Deserialize<ShipmentQuery>(serialized, options);

        if (deserialized is FcAllocationRefQuery q)

        {

            // do something with derived type

            Console.WriteLine(string.Join(", ", q.FcAllocationReferenceIds));

        }

        // At this point you can ship `deserialized` off to Mediator.Send and either handle the base type or have separate handlers for each derived type

        // Register the options so that ASP.NET uses it for parameter binding:

        // services.Configure<JsonOptions>(options =>

        // {

        //   options.JsonSerializerOptions.Converters.Add(new OneOfJsonConverterFactory());

        // });

    }

}