Question

有没有办法从JsonSerializer课程中取出设置，并在新的JsonSerializer中重新实现这些设置？

似乎没有任何方法可以做任何类似的事情。我找到的最好的是通过反射调用的私有方法ApplySerializerSettings。

我正在尝试从WriteJson方法中获取序列化程序并将其复制到新的序列化程序中，稍微调整一下。具体来说，我想替换ContractResolver。

public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

Answer 1

似乎最好的方法是将所有设置复制到新对象中。它们有很多，所以这里有一个很好的扩展方法（从8.0.3开始）。

public static class JsonSerializerExtensions
{
  public static JsonSerializer DeepCopy(this JsonSerializer serializer)
  {
    var copiedSerializer = new JsonSerializer
    {
      Context = serializer.Context,
      Culture = serializer.Culture,
      ContractResolver = serializer.ContractResolver,
      ConstructorHandling = serializer.ConstructorHandling,
      CheckAdditionalContent = serializer.CheckAdditionalContent,
      DateFormatHandling = serializer.DateFormatHandling,
      DateFormatString = serializer.DateFormatString,
      DateParseHandling = serializer.DateParseHandling,
      DateTimeZoneHandling = serializer.DateTimeZoneHandling,
      DefaultValueHandling = serializer.DefaultValueHandling,
      EqualityComparer = serializer.EqualityComparer,
      FloatFormatHandling = serializer.FloatFormatHandling,
      Formatting = serializer.Formatting,
      FloatParseHandling = serializer.FloatParseHandling,
      MaxDepth = serializer.MaxDepth,
      MetadataPropertyHandling = serializer.MetadataPropertyHandling,
      MissingMemberHandling = serializer.MissingMemberHandling,
      NullValueHandling = serializer.NullValueHandling,
      ObjectCreationHandling = serializer.ObjectCreationHandling,
      PreserveReferencesHandling = serializer.PreserveReferencesHandling,
      ReferenceResolver = serializer.ReferenceResolver,
      ReferenceLoopHandling = serializer.ReferenceLoopHandling,
      StringEscapeHandling = serializer.StringEscapeHandling,
      TraceWriter = serializer.TraceWriter,
      TypeNameHandling = serializer.TypeNameHandling,
      SerializationBinder = serializer.SerializationBinder,
      TypeNameAssemblyFormatHandling = serializer.TypeNameAssemblyFormatHandling
    };
    foreach (var converter in serializer.Converters)
    {
      copiedSerializer.Converters.Add(converter);
    }
    return copiedSerializer;
  }
}

这很难看，但至少你只需要写一次。要小心，因为属性本身不会被深层复制。

根据您的实施，下面的答案是不稳定的，特别是在解决合同时。保持它，以防它有助于某人。

所以，我无法完全复制设置，但我找到了一个可能需要考虑的好工作。您可以在锁定的上下文中设置要更改的属性，然后在之后重置它们。

public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
    var thing = value as IThing;

    if (thing == null)
        throw new ArgumentException($"Writing Json failed because " + 
          "value was not a 'Thing' of type, {typeof(IThing).FullName}");

    JObject jsonThing;
    //If your solution is multithreaded,
    //and is using a shared serializer (which you probably are),
    //you should lock the serializer so that it doesn't accidentally use 
    //the "CustomObjectResolver"
    lock (serializer)
    {
        //Hold the original value(s) to reset later
        var originalContractResolver = serializer.ContractResolver;
        //Set custom value(s)
        serializer.ContractResolver = new CustomObjectResolver();
        //Serialization with custom properties
        jsonThing = JObject.FromObject(value, serializer);
        //Reset original value(s)
        serializer.ContractResolver = originalContractResolver;
    }

    //Finish serializing and write to writer.
}

Answer 2

不确定这是否是主题-但这是我在Google中搜索 Clone JSONSerializerSettings 时出现的第一篇文章，我想我会留个通知。

我刚刚有一个类似的要求。

在我的.Net Core WebApi解决方案中，我们有使用

序列化JSON的默认设置

jsonSerializaerSettings.NullValueHandling = NullValueHandling.Ignore;

但是在一些端点中，我也想序列化null属性，因为这些端点代表一个数据集。因此，所有对象在序列化时都应具有所有属性。

我尝试了几种方法，然后阅读了Options模式，偶然发现了IOptionSnapshot-https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options?view=aspnetcore-2.1#reload-configuration-data-with-ioptionssnapshot

所以我最终将IOptionsSnapshot注入到我的控制器方法中，这为我提供了默认选项的副本，我可以修改该默认选项并将其用于单个请求。

并在下一个请求时，注入的选项恢复为默认值。

好又容易-至少出于我的目的。

所以我样品的最终解决方案是这样

[HttpPost("dataset", Name = "GetReportDataset")]
public IActionResult GetReportDataset(
    [FromServices]IOptionsSnapshot<MvcJsonOptions> jsonOptions,
    [FromBody]DataSetReport report,
    [FromQuery]int? top)
{
    //Logic to fetch dataset
    var myDataSet = myRepository.GetDataset(report, top);

    var serializerSettings = jsonOptions.Value.SerializerSettings;
    serializerSettings.NullValueHandling = NullValueHandling.Include;

    return new JsonResult(myDataSet, serializerSettings);
}

希望这可以帮助其他人来这里使用类似的东西。

/安德斯

将JsonSerializerSettings从JsonSerializer复制到新的JsonSerializer

2 个答案: