在项目的模型我使用的是JsonConverter属性，以帮助这些模型的（反）序列。
该转换器目前看起来是这样的：
public class CustomJsonConverter : Newtonsoft.Json.JsonConverter
{
bool _canWrite = true;
public override bool CanWrite
{
get { return _canWrite; }
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
serializer.PreserveReferencesHandling = PreserveReferencesHandling.Objects;
serializer.DefaultValueHandling = DefaultValueHandling.Ignore;
serializer.NullValueHandling = NullValueHandling.Ignore;
_canWrite = false;
var jObject = JObject.FromObject(value, serializer);
_canWrite = true;
jObject.WriteTo(writer);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
serializer.PreserveReferencesHandling = PreserveReferencesHandling.Objects;
if (reader.TokenType == JsonToken.StartObject)
{
existingValue = existingValue ?? serializer.ContractResolver.ResolveContract(objectType).DefaultCreator();
serializer.Populate(reader, existingValue);
return existingValue;
}
else if (reader.TokenType == JsonToken.Null)
{
return null;
}
else
{
throw new JsonSerializationException();
}
}
public override bool CanConvert(Type objectType)
{
return typeof(IModelBase).IsAssignableFrom(objectType);
}
}
该机型有一个基类，看起来像这样：
[JsonConverter(typeof(CustomJsonConverter))]
public abstract class ModelBase : IModelBase
{
public string ID { get; set; }
public DateTime CreatedAt { get; set; }
public DateTime ModifiedAt { get; set; }
}
所述ModelBase类的派生类具有的类型也从ModelBase派生属性。例如：
public class CustomerModel : ModelBase
{
public string Name { get; set; }
public UserModel CreatedBy { get; set; }
public UserModel ModifiedBy { get; set; }
}
public class UserModel : ModelBase
{
public string Name { get; set; }
public UserModel CreatedBy { get; set; }
public UserModel ModifiedBy { get; set; }
}
我在ASP.NET Web API 2应用程序（服务器端），并在C＃应用程序（客户端）使用这些模型。对于大多数API调用，则返回的车型阵列。当序列化的模型，东西正常工作。然而，反序列化时，仅每参考的第一次出现充满的信息。
[
{
"$id": "1",
"Name": "Customer1",
"CreatedBy": {
"$id": "2",
"ID": "1",
"Name": "User1"
},
"ModifiedBy": {
"$id": "3",
"ID": "3",
"Name": "User3"
},
"ID": "1",
"CreatedAt": "2019-02-06T00:00:04",
"ModifiedAt": "2019-02-06T00:20:12"
},
{
"$id": "4",
"Name": "Customer2",
"CreatedBy": {
"$ref": "2"
},
"ModifiedBy": {
"$ref": "2"
},
"ID": "2",
"CreatedAt": "2019-02-06T00:10:00",
"ModifiedAt": "2019-02-06T00:10:00"
}
]
当尝试反序列化由Web API返回此JSON对象中，CreatedBy和ModifiedBy性能将是第一CustomerModel对象正确。对于第二CustomerModel对象，但是，这些属性将不设置任何性质的新UserModel实例。
反序列化JSON字符串，我使用下面的代码：
using (var sr = new StreamReader(streamFromWebAPICall))
{
using (var jtr = new JsonTextReader(sr))
{
var js = new JsonSerializer();
return js.Deserialize(jtr, objectType);
}
}
我能做些什么在所有反序列化对象设置正确的属性？
这个问题似乎是在serializer.Populate(reader, existingValue)，其中引用不记得。
你的基本问题是，你提供的类型，你还想要启用custom JsonConverter一个PreserveReferencesHandling。但每当应用自定义转换器，必须手动打理一切，包括分析和"$ref"和"$id"性质发生。您的转换并没有这样做，因此您的反序列化的代码不正确地反序列化对象图。
该accepted answer到Custom object serialization vs PreserveReferencesHandling包括模板转换器，显示了这些特性可以处理。然而，由于你的转换器似乎只前（反）序列被触发一些串行设置，你可以简单地拨打电话，以递归（德）序列化对象，禁用该转换器的时间，就像这样：
public class CustomJsonConverter : Newtonsoft.Json.JsonConverter
{
[ThreadStatic]
static bool disabled;
// Disables the converter in a thread-safe manner.
bool Disabled { get { return disabled; } set { disabled = value; } }
public override bool CanWrite { get { return !Disabled; } }
public override bool CanRead { get { return !Disabled; } }
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
using (new PushValue<bool>(true, () => Disabled, val => Disabled = val))
using (new PushValue<PreserveReferencesHandling>(PreserveReferencesHandling.Objects, () => serializer.PreserveReferencesHandling, val => serializer.PreserveReferencesHandling = val))
using (new PushValue<DefaultValueHandling>(DefaultValueHandling.Ignore, () => serializer.DefaultValueHandling, val => serializer.DefaultValueHandling = val))
using (new PushValue<NullValueHandling>(NullValueHandling.Ignore, () => serializer.NullValueHandling, val => serializer.NullValueHandling = val))
{
serializer.Serialize(writer, value);
}
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
if (reader.TokenType == JsonToken.Null)
{
return null;
}
using (new PushValue<bool>(true, () => Disabled, val => Disabled = val))
using (new PushValue<PreserveReferencesHandling>(PreserveReferencesHandling.Objects, () => serializer.PreserveReferencesHandling, val => serializer.PreserveReferencesHandling = val))
using (new PushValue<DefaultValueHandling>(DefaultValueHandling.Ignore, () => serializer.DefaultValueHandling, val => serializer.DefaultValueHandling = val))
using (new PushValue<NullValueHandling>(NullValueHandling.Ignore, () => serializer.NullValueHandling, val => serializer.NullValueHandling = val))
{
return serializer.Deserialize(reader, objectType);
}
}
public override bool CanConvert(Type objectType)
{
throw new NotImplementedException();
}
}
public struct PushValue<T> : IDisposable
{
Action<T> setValue;
T oldValue;
public PushValue(T value, Func<T> getValue, Action<T> setValue)
{
if (getValue == null || setValue == null)
throw new ArgumentNullException();
this.setValue = setValue;
this.oldValue = getValue();
setValue(value);
}
// By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.
public void Dispose()
{
if (setValue != null)
setValue(oldValue);
}
}
请注意，禁用该转换器的逻辑需要进行线程安全的，因为Json.NET将分享跨线程合同和转换器。
演示小提琴＃1 here。
作为替代方案，可以完全消除转换器和直接应用到[JsonObject(IsReference = true)] ModelBase：
[JsonObject(IsReference = true)]
public abstract class ModelBase : IModelBase
{
public string ID { get; set; }
public DateTime CreatedAt { get; set; }
public DateTime ModifiedAt { get; set; }
}
然后序列化与DefaultValueHandling.Ignore在像这样设置中指定NullValueHandling.Ignore反序列化：
static object Deserialize(Stream streamFromWebAPICall, Type objectType)
{
using (var sr = new StreamReader(streamFromWebAPICall))
{
using (var jtr = new JsonTextReader(sr))
{
var settings = new JsonSerializerSettings
{
DefaultValueHandling = DefaultValueHandling.Ignore,
NullValueHandling = NullValueHandling.Ignore,
};
var js = JsonSerializer.CreateDefault(settings);
return js.Deserialize(jtr, objectType);
}
}
}
演示小提琴＃2 here。
请注意，您还可以设置[JsonObject(ItemNullValueHandling = NullValueHandling.Ignore)]为Json.NET 11.0.1的，但似乎没有要在ItemDefaultValueHandling的JsonObjectAttribute设置，因此增加，为串行设置（或使用nullables可选值类型的值，如CreatedAt）是必需的。