Feature/aot (#232)

AOT support

CryptoExchange.Net/Converters/SystemTextJson/NullableEnumConverterFactory.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Text.Json.Serialization.Metadata;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace CryptoExchange.Net.Converters.SystemTextJson
+{
+    internal class NullableEnumConverterFactory : JsonConverterFactory
+    {
+        private readonly IJsonTypeInfoResolver _jsonTypeInfoResolver;
+        private static readonly JsonSerializerOptions _options = new JsonSerializerOptions();
+
+        public NullableEnumConverterFactory(IJsonTypeInfoResolver jsonTypeInfoResolver)
+        {
+            _jsonTypeInfoResolver = jsonTypeInfoResolver;
+        }
+
+        public override bool CanConvert(Type typeToConvert)
+        {
+            var b = Nullable.GetUnderlyingType(typeToConvert);
+            if (b == null)
+                return false;
+
+            var typeInfo = _jsonTypeInfoResolver.GetTypeInfo(b, _options);
+            if (typeInfo == null)
+                return false;
+
+            return typeInfo.Converter is INullableConverterFactory;
+        }
+
+        public override JsonConverter? CreateConverter(Type typeToConvert, JsonSerializerOptions options)
+        {
+            var b = Nullable.GetUnderlyingType(typeToConvert) ?? throw new ArgumentNullException($"Not nullable {typeToConvert.Name}");
+            var typeInfo = _jsonTypeInfoResolver.GetTypeInfo(b, _options) ?? throw new ArgumentNullException($"Can find type {typeToConvert.Name}");
+            if (typeInfo.Converter is not INullableConverterFactory nullConverterFactory)
+                throw new ArgumentNullException($"Can find type converter for {typeToConvert.Name}");
+            
+            return nullConverterFactory.CreateNullableConverter();
+        }
+    }
+}