NewtonSoft.Json 具有 IEnumerable<ISomeInterface> 类型属性的序列化和反序列化类

NewtonSoft.Json Serialize and Deserialize class with property of type IEnumerablelt;ISomeInterfacegt;(NewtonSoft.Json 具有 IEnumerablelt;ISomeInterfacegt; 类型属性的序列化和反序列化类)

问题描述

我正在尝试移动一些代码以使用 ASP.NET MVC Web API 生成的 Json 数据而不是 SOAP Xml.

I am trying to move some code to consume ASP.NET MVC Web API generated Json data instead of SOAP Xml.

我在序列化和反序列化以下类型的属性时遇到了问题:

I have run into a problem with serializing and deserializing properties of type:

IEnumerable<ISomeInterface>.

这是一个简单的例子:

public interface ISample{
  int SampleId { get; set; }
}
public class Sample : ISample{
  public int SampleId { get; set; }
}
public class SampleGroup{
  public int GroupId { get; set; }
  public IEnumerable<ISample> Samples { get; set; }
 }
}

我可以通过以下方式轻松序列化 SampleGroup 的实例:

I can serialize instances of SampleGroup easily with:

var sz = JsonConvert.SerializeObject( sampleGroupInstance );

但是对应的反序列化失败了:

However the corresponding deserialize fails:

JsonConvert.DeserializeObject<SampleGroup>( sz );

带有此异常消息:

无法创建 JsonSerializationExample.ISample 类型的实例.类型是接口或抽象类，无法实例化."

"Could not create an instance of type JsonSerializationExample.ISample. Type is an interface or abstract class and cannot be instantated."

如果我派生一个 JsonConverter，我可以如下装饰我的属性:

If I derive a JsonConverter I can decorate my property as follows:

[JsonConverter( typeof (SamplesJsonConverter) )]
public IEnumerable<ISample> Samples { get; set; }

这是 JsonConverter:

Here is the JsonConverter:

public class SamplesJsonConverter : JsonConverter{
  public override bool CanConvert( Type objectType ){
    return ( objectType == typeof (IEnumerable<ISample>) );
  }

  public override object ReadJson( JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer ){
    var jA = JArray.Load( reader );
    return jA.Select( jl => serializer.Deserialize<Sample>( new JTokenReader( jl ) ) ).Cast<ISample>( ).ToList( );
  }

  public override void WriteJson( JsonWriter writer, object value, JsonSerializer serializer ){
    ... What works here?
  }
}

这个转换器解决了反序列化问题，但我不知道如何编写 WriteJson 方法以使序列化再次工作.

This converter solves the deserialization problem but I cannot figure how to code the WriteJson method to get serialization working again.

有人可以帮忙吗?

这是解决问题的正确"方法吗?

Is this a "correct" way to solve the problem in the first place?

推荐答案

你不需要使用 JsonConverterAttribute，只要保持你的模型干净，使用 CustomCreationConverter，代码更简单:

You don't need to use JsonConverterAttribute, just keep your model clean and use CustomCreationConverter instead, the code is simpler:

public class SampleConverter : CustomCreationConverter<ISample>
{
    public override ISample Create(Type objectType)
    {
        return new Sample();
    }
}

然后:

var sz = JsonConvert.SerializeObject( sampleGroupInstance );
JsonConvert.DeserializeObject<SampleGroup>( sz, new SampleConverter());

文档:使用 CustomCreationConverter 反序列化

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