Question

我的数据库中的日期存储为Utc。但是当我用实体框架来修复它们时，它们就是未指定的类型。

当JSON.Net序列化它们时，它们不是Utc格式。有没有办法告诉JSON.Net将DateTimes序列化为Utc，即使它们的类型未指定为Utc？

Answer 1

将DateTimeZoneHandling上的JsonSerializerSettings设置为Utc。这将在序列化之前将所有日期转换为UTC。

public void SerializeObjectDateTimeZoneHandling()
{
  string json = JsonConvert.SerializeObject(
    new DateTime(2000, 1, 1, 1, 1, 1, DateTimeKind.Unspecified),
    new JsonSerializerSettings
    {
      DateTimeZoneHandling = DateTimeZoneHandling.Utc
    });

  Assert.AreEqual(@"""2000-01-01T01:01:01Z""", json);
}

文档：DateTimeZoneHandling setting

Answer 2

正如@dez在评论中提到的那样，您可以直接从.NET代码中直接在.net代码中将DateTime对象“标记”为UTC，然后再从数据库中加载它们并进行序列化之前：

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Answer 3

对我来说，为DateTime属性创建UTC转换器（基于Newtonsoft.Json.Converters.IsoDateTimeConverter的实现）更为简单。

public class UtcJsonDateTimeConverter : DateTimeConverterBase
{
    private const string DefaultDateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFFZ";

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        string text;

        if (value is DateTime dateTime)
        {
            text = dateTime.ToString(DefaultDateTimeFormat, CultureInfo.InvariantCulture);
        }
        else
        {
            throw new JsonSerializationException(
                $"Unexpected value when converting date. Expected DateTime or DateTimeOffset, got {value.GetType()}.");
        }

        writer.WriteValue(text);
    }

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

            return null;
        }

        if (reader.TokenType == JsonToken.Date)
        {
            return reader.Value;
        }
        else if (reader.TokenType != JsonToken.String)
        {
            throw new JsonSerializationException($"Unexpected token parsing date. Expected String, got {reader.TokenType}.");
        }

        string date_text = reader.Value.ToString();

        if (string.IsNullOrEmpty(date_text) && nullable)
        {
            return null;
        }

        return DateTime.Parse(date_text, CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
    }
}

public class SomeEntity
{

   [JsonProperty(PropertyName = "id", Order = 1)]
   public int ID { get; set; }

   [JsonProperty(PropertyName = "created", Order = 2)]
   [JsonConverter(typeof(UtcJsonDateTimeConverter))]
   public DateTime Created { get; set; }
}

Answer 4

我使用了可接受的答案，但是将其应用于默认设置：

        JsonConvert.DefaultSettings = (() =>
        {
            var settings = new JsonSerializerSettings();
            settings.Converters.Add(new StringEnumConverter());
            settings.Formatting = Formatting.Indented;
            settings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
            return settings;
        });

即使未指定，你能告诉JSON.Net将DateTime序列化为Utc吗？

4 个答案: