JsonEnumMemberStringEnumConverter.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text;
using System.Text.Json.Serialization;
using System.Text.Json;
using System.Threading.Tasks;

namespace ApiGenerator {
    using System.Reflection;
    using System.Text.Json;
    using System.Text.Json.Serialization;
    using System.Xml.Linq;

    public static class EnumExtensions {
        public static TAttribute GetAttribute<TAttribute>(this Enum value)
            where TAttribute : System.Attribute {
            var type = value.GetType();
            var name = Enum.GetName(type, value);
            if(name == null) {
                throw new JsonException();
            }
            var attr = type.GetField(name)? // I prefer to get attributes this way
                .GetCustomAttribute<TAttribute>();
            if (attr == null) {
                throw new JsonException();
            }
            return attr;
        }
    }
    [System.AttributeUsage(System.AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
    public class JsonEnumNameAttribute : System.Attribute {
        public string JsonName { get; private set; }
        public JsonEnumNameAttribute(string jsonName) {
            JsonName = jsonName;
        }
    }
    public class DictionaryTKeyEnumTValueConverter : JsonConverterFactory {
        public override bool CanConvert(Type typeToConvert) {
            if (!typeToConvert.IsGenericType) {
                return false;
            }

            if (typeToConvert.GetGenericTypeDefinition() != typeof(Dictionary<,>)) {
                return false;
            }

            return typeToConvert.GetGenericArguments()[0].IsEnum;
        }

        public override JsonConverter CreateConverter(Type type, JsonSerializerOptions options) {
            Type keyType = type.GetGenericArguments()[0];
            Type valueType = type.GetGenericArguments()[1];

            var converter = Activator.CreateInstance(
                typeof(DictionaryEnumConverterInner<,>).MakeGenericType(
                    new Type[] { keyType, valueType }),
                BindingFlags.Instance | BindingFlags.Public,
                binder: null,
                args: new object[] { options },
                culture: null);
            if(converter == null) {
                throw new Exception("Error creating converter for type " + type.ToString());
            }
            return (JsonConverter)converter;
        }

        private class DictionaryEnumConverterInner<TKey, TValue> :
            JsonConverter<Dictionary<TKey, TValue>> where TKey : struct, Enum {
            private readonly JsonConverter<TValue> _valueConverter;
            private readonly Type _keyType;
            private readonly Type _valueType;

            public DictionaryEnumConverterInner(JsonSerializerOptions options) {
                // For performance, use the existing converter.
                _valueConverter = (JsonConverter<TValue>)options
                    .GetConverter(typeof(TValue));

                // Cache the key and value types.
                _keyType = typeof(TKey);
                _valueType = typeof(TValue);
            }

            public override Dictionary<TKey, TValue> Read(
                ref Utf8JsonReader reader,
                Type typeToConvert,
                JsonSerializerOptions options) {
                if (reader.TokenType != JsonTokenType.StartObject) {
                    throw new JsonException();
                }

                var dictionary = new Dictionary<TKey, TValue>();

                while (reader.Read()) {
                    if (reader.TokenType == JsonTokenType.EndObject) {
                        return dictionary;
                    }

                    // Get the key.
                    if (reader.TokenType != JsonTokenType.PropertyName) {
                        throw new JsonException();
                    }

#pragma warning disable CS8600 // Converting null literal or possible null value to non-nullable type.
                    string propertyName = reader.GetString();
#pragma warning restore CS8600 // Converting null literal or possible null value to non-nullable type.

                    // For performance, parse with ignoreCase:false first.
                    if (!Enum.TryParse(propertyName, ignoreCase: false, out TKey key) &&
                        !Enum.TryParse(propertyName, ignoreCase: true, out key)) {
                        throw new JsonException(
                            $"Unable to convert \"{propertyName}\" to Enum \"{_keyType}\".");
                    }

                    // Get the value.
                    reader.Read();
                    var value = _valueConverter.Read(ref reader, _valueType, options);
                    if(value == null) {
                        throw new JsonException();
                    }
                    // Add to dictionary.
                    dictionary.Add(key, value);
                }

                throw new JsonException();
            }

            public override void Write(
                Utf8JsonWriter writer,
                Dictionary<TKey, TValue> dictionary,
                JsonSerializerOptions options) {
                writer.WriteStartObject();

                //foreach ((TKey key, TValue value) in dictionary) {
                foreach (var item in dictionary) {
                    var propertyName = item.Key.ToString();
                    writer.WritePropertyName
                        (options.PropertyNamingPolicy?.ConvertName(propertyName) ?? propertyName);

                    _valueConverter.Write(writer, item.Value, options);
                }

                writer.WriteEndObject();
            }
        }

    }
    public class JsonEnumMemberStringEnumConverter : JsonConverterFactory {
        // TODO: Implement JsonEnumMemberStringEnumConverter
        public override bool CanConvert(Type typeToConvert) {
             return typeToConvert.IsEnum;
        }
        public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options) {
            //Type keyType = typeToConvert.GetGenericArguments()[0];
            //Type valueType = typeToConvert.GetGenericArguments()[1];

            var converter = Activator.CreateInstance(
                typeof(EnumConverterInner<>).MakeGenericType(typeToConvert));

            //    new Type[] { typeToConvert }),
            //BindingFlags.Instance | BindingFlags.Public,
            //binder: null,
            //args: new object[] { options },
            //culture: null);
            if(converter == null ) {
                throw new JsonException();
            }
            return (JsonConverter)converter;
        }
        private class EnumConverterInner<TKey> :
            JsonConverter<TKey> where TKey : struct, Enum {
            public override TKey Read(
                ref Utf8JsonReader reader,
                Type typeToConvert,
                JsonSerializerOptions options) {
                if (reader.TokenType != JsonTokenType.String) {
                    throw new JsonException();
                }

                //TKey dictionary = new TKey();

                //while (reader.Read()) {
                //                    if (reader.TokenType == JsonTokenType.EndObject) {
                //                        return dictionary;
                //                    }

                // Get the key.
                //                    if (reader.TokenType != JsonTokenType.PropertyName) {
                //                        throw new JsonException();
                //                    }
                
                string? item = reader.GetString();
                TKey value;
                if(Enum.TryParse<TKey>(item, out value)) {
                    return value;
                }
                foreach (var name in typeToConvert.GetEnumNames()) {
                    var field = typeToConvert.GetField(name);
                    if (field?.GetCustomAttribute<JsonEnumNameAttribute>()?.JsonName == item) {
                        return (TKey)Enum.Parse(typeToConvert, name);
                    }
                }
                //// For performance, parse with ignoreCase:false first.
                //if (!Enum.TryParse(item, ignoreCase: false, out TKey key) &&
                //        !Enum.TryParse(item, ignoreCase: true, out key)) {
                //        throw new JsonException(
                //            $"Unable to convert \"{item}\" to Enum \"{typeToConvert}\".");
                //    }
                //    // Get the value.
                //    //reader.Read();
                //    return key;
                //}
                throw new JsonException();

            }
            public override void Write(
                Utf8JsonWriter writer,
                TKey item,
                JsonSerializerOptions options) {
                //writer.WriteStartObject();

                //foreach ((TKey key, TValue value) in dictionary) {
                //foreach (var item in dictionary) {
                    var propertyName = item.ToString();
                    var attr = item.GetAttribute<JsonEnumNameAttribute>();
                if (attr != null) {
                    writer.WriteStringValue(attr.JsonName);
                }
                else {
                    writer.WriteStringValue(propertyName);
                }
                        //(options.PropertyNamingPolicy?.ConvertName(propertyName) ?? propertyName);

                    //_valueConverter.Write(writer, item.Value, options);
                //}

                //writer.WriteEndObject();
            }
        }
    }
}