Added System.Text.Json ArrayConverter Write implementation

CryptoExchange.Net.UnitTests/SystemTextJsonConverterTests.cs

@@ -5,6 +5,8 @@ using NUnit.Framework;
 using System;
 using System.Text.Json.Serialization;
 using NUnit.Framework.Legacy;
+using CryptoExchange.Net.Converters;
+using CryptoExchange.Net.Testing.Comparers;
 
 namespace CryptoExchange.Net.UnitTests
 {
@@ -242,6 +244,44 @@ namespace CryptoExchange.Net.UnitTests
             var result = JsonSerializer.Deserialize<STJDecimalObject>("{ \"test\": " + value + "}");
             Assert.That(result.Test, Is.EqualTo(expected == -999 ? decimal.MaxValue : expected));
         }
+
+        [Test()]
+        public void TestArrayConverter()
+        {
+            var data = new Test()
+            {
+                Prop1 = 2,
+                Prop2 = null,
+                Prop3 = "123",
+                Prop3Again = "123",
+                Prop4 = null,
+                Prop5 = new Test2
+                {
+                    Prop21 = 3,
+                    Prop22 = "456"
+                },
+                Prop6 = new Test3
+                {
+                    Prop31 = 4,
+                    Prop32 = "789"
+                },
+                Prop7 = TestEnum.Two
+            };
+
+            var serialized = JsonSerializer.Serialize(data);
+            var deserialized = JsonSerializer.Deserialize<Test>(serialized);
+
+            Assert.That(deserialized.Prop1, Is.EqualTo(2));
+            Assert.That(deserialized.Prop2, Is.Null);
+            Assert.That(deserialized.Prop3, Is.EqualTo("123"));
+            Assert.That(deserialized.Prop3Again, Is.EqualTo("123"));
+            Assert.That(deserialized.Prop4, Is.Null);
+            Assert.That(deserialized.Prop5.Prop21, Is.EqualTo(3));
+            Assert.That(deserialized.Prop5.Prop22, Is.EqualTo("456"));
+            Assert.That(deserialized.Prop6.Prop31, Is.EqualTo(4));
+            Assert.That(deserialized.Prop6.Prop32, Is.EqualTo("789"));
+            Assert.That(deserialized.Prop7, Is.EqualTo(TestEnum.Two));
+        }
     }
 
     public class STJDecimalObject
@@ -281,4 +321,42 @@ namespace CryptoExchange.Net.UnitTests
         [JsonConverter(typeof(BoolConverter))]
         public bool Value { get; set; }
     }
+
+    [JsonConverter(typeof(ArrayConverter))]
+    record Test
+    {
+        [ArrayProperty(0)]
+        public int Prop1 { get; set; }
+        [ArrayProperty(1)]
+        public int? Prop2 { get; set; }
+        [ArrayProperty(2)]
+        public string Prop3 { get; set; }
+        [ArrayProperty(2)]
+        public string Prop3Again { get; set; }
+        [ArrayProperty(3)]
+        public string Prop4 { get; set; }
+        [ArrayProperty(4)]
+        public Test2 Prop5 { get; set; }
+        [ArrayProperty(5)]
+        public Test3 Prop6 { get; set; }
+        [ArrayProperty(6), JsonConverter(typeof(EnumConverter))]
+        public TestEnum? Prop7 { get; set; }
+    }
+
+    [JsonConverter(typeof(ArrayConverter))]
+    record Test2
+    {
+        [ArrayProperty(0)]
+        public int Prop21 { get; set; }
+        [ArrayProperty(1)]
+        public string Prop22 { get; set; }
+    }
+
+    record Test3
+    {
+        [JsonPropertyName("prop31")]
+        public int Prop31 { get; set; }
+        [JsonPropertyName("prop32")]
+        public string Prop32 { get; set; }
+    }
 }

CryptoExchange.Net/Converters/SystemTextJson/ArrayConverter.cs

@@ -42,8 +42,63 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
 
             public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
             {
-                // TODO
+                if (value == null)
-                throw new NotImplementedException();
+                {
+                    writer.WriteNullValue();
+                    return;
+                }
+
+                writer.WriteStartArray();
+
+                var valueType = value.GetType();
+                if (!_typeAttributesCache.TryGetValue(valueType, out var typeAttributes))
+                    typeAttributes = CacheTypeAttributes(valueType);
+
+                var ordered = typeAttributes.Where(x => x.ArrayProperty != null).OrderBy(p => p.ArrayProperty.Index);
+                var last = -1;
+                foreach (var prop in ordered)
+                {
+                    if (prop.ArrayProperty.Index == last)
+                        continue;
+
+                    while (prop.ArrayProperty.Index != last + 1)
+                    {
+                        writer.WriteNullValue();
+                        last += 1;
+                    }
+
+                    last = prop.ArrayProperty.Index;
+
+                    var objValue = prop.PropertyInfo.GetValue(value);
+                    if (objValue == null)
+                    {
+                        writer.WriteNullValue();
+                        continue;
+                    }
+
+                    JsonSerializerOptions? typeOptions = null;
+                    if (prop.JsonConverterType != null)
+                    {
+                        var converter = (JsonConverter)Activator.CreateInstance(prop.JsonConverterType);
+                        typeOptions = new JsonSerializerOptions();
+                        typeOptions.Converters.Clear();
+                        typeOptions.Converters.Add(converter);
+                    }
+
+                    if (prop.JsonConverterType == null && IsSimple(prop.PropertyInfo.PropertyType))
+                    {
+                        if (prop.PropertyInfo.PropertyType == typeof(string))
+                            writer.WriteStringValue(Convert.ToString(objValue, CultureInfo.InvariantCulture));
+                        else
+                            writer.WriteRawValue(Convert.ToString(objValue, CultureInfo.InvariantCulture));
+                    }
+                    else
+                    {
+                        JsonSerializer.Serialize(writer, objValue, typeOptions ?? options);
+                    }
+                }
+
+                writer.WriteEndArray();
             }
 
             /// <inheritdoc />
@@ -56,6 +111,19 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                 return (T)ParseObject(ref reader, result, typeToConvert);
             }
 
+            private static bool IsSimple(Type type)
+            {
+                if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
+                {
+                    // nullable type, check if the nested type is simple.
+                    return IsSimple(type.GetGenericArguments()[0]);
+                }
+                return type.IsPrimitive
+                  || type.IsEnum
+                  || type == typeof(string)
+                  || type == typeof(decimal);
+            }
+
             private static List<ArrayPropertyInfo> CacheTypeAttributes(Type type)
             {
                 var attributes = new List<ArrayPropertyInfo>();
@@ -71,7 +139,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                         ArrayProperty = att,
                         PropertyInfo = property,
                         DefaultDeserialization = property.GetCustomAttribute<JsonConversionAttribute>() != null,
-                        JsonConverterType = property.GetCustomAttribute<JsonConverterAttribute>()?.ConverterType,
+                        JsonConverterType = property.GetCustomAttribute<JsonConverterAttribute>()?.ConverterType ?? property.PropertyType.GetCustomAttribute<JsonConverterAttribute>()?.ConverterType,
                         TargetType = Nullable.GetUnderlyingType(property.PropertyType) ?? property.PropertyType
                     });
                 }
@@ -126,6 +194,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                                 JsonTokenType.True => true,
                                 JsonTokenType.String => reader.GetString(),
                                 JsonTokenType.Number => reader.GetDecimal(),
+                                JsonTokenType.StartObject => JsonSerializer.Deserialize(ref reader, attribute.TargetType),
                                 _ => throw new NotImplementedException($"Array deserialization of type {reader.TokenType} not supported"),
                             };
                         }