c# - JsonConverter 不作为属性属性

Question

我有一个对象，其中包含一个具有 JsonConverter 属性的属性。对于数据读写，转换器不工作。声明的属性是

[JsonConverter(typeof(EpochDateTimeConverter))]
public DateTime CreatedOn { get; set; } 

EpochDateTimeConverter 是

public class EpochDateTimeConverter : DateTimeConverterBase
    {
        private static readonly DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            if (value == null)
            {
                writer.WriteNull();
                return;
            }

            long millisecondsSinceEpoch;
            if (value is DateTime)
            {
                millisecondsSinceEpoch = Convert.ToInt64((((DateTime)value).ToUniversalTime() - epoch).TotalMilliseconds);
            }
            else
            {
                if (!(value is DateTimeOffset))
                    throw new JsonSerializationException("Expected date object value.");
                millisecondsSinceEpoch = Convert.ToInt64((((DateTimeOffset)value).ToUniversalTime().UtcDateTime - epoch).TotalMilliseconds);
            }
            writer.WriteValue(millisecondsSinceEpoch);
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            if (reader.TokenType == JsonToken.Null)
            {
                if (objectType != typeof(DateTime?) && objectType != typeof(DateTimeOffset?))
                    throw new JsonSerializationException($"Cannot convert null value to {objectType}");

                return null;
            }
            if (reader.TokenType == JsonToken.Integer || reader.TokenType == JsonToken.Float)
            {
                var millisecondsSinceEpoch = (long)reader.Value;
                var dateTime = FromUnixTime(millisecondsSinceEpoch);
                if (objectType == typeof(DateTime) || objectType == typeof(DateTime?))
                {
                    return dateTime;
                }
                else
                {
                    return new DateTimeOffset(dateTime);
                }
            }
            if (reader.TokenType == JsonToken.Date || reader.TokenType == JsonToken.Float)
            {
                return ConvertToUnixTimestamp(Convert.ToDateTime(reader.Value));
            }
            throw new JsonSerializationException($"Cannot convert to DateTime or DateTimeOffset from token type {reader.TokenType}");
        }
        private static DateTime FromUnixTime(long unixTime)
        {
            try
            {
                return epoch.AddSeconds(unixTime);
            }
            catch(Exception)
            {
                unixTime = unixTime / 1000;
                return epoch.AddSeconds(unixTime);
            }

        }

        public static double ConvertToUnixTimestamp(DateTime date)
        {
            DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            TimeSpan diff = date.ToUniversalTime() - origin;
            return Math.Floor(diff.TotalSeconds);
        }

    }

我无法得到错误。但是 EpochDateTimeConverter 不会自动调用。我不明白出了什么问题。谁能帮帮我？

Answer 1

确保使用 System.Text.Json.Serialization 而不是 Newtonsoft.Json。