[英]Web API2 Serialization exception
我有一个使用EF搭建的Web api2应用程序。
我正在尝试序列化以下类(其中包含延迟加载的导航属性):
namespace Models
{
public class Speciality
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int SpecialityId { get; set; }
public string Name { get; set; }
public virtual ICollection<Doctor> Doctors { get; set; }
public virtual ICollection<MedicalFacility> MedicalFacilities { get; set; }
}
}
这是我的控制器:
namespace FindAMedicService.Controllers
{
public class SpecialitiesController : ApiController
{
private ApplicationDbContext db = new ApplicationDbContext();
// GET: api/Specialities
public IQueryable<Speciality> GetSpeciality()
{
return db.Speciality;
}
}
}
当我尝试访问此特定服务以获取“特色”列表时,出现以下错误:
<Error>
<Message>An error has occurred.</Message>
<ExceptionMessage>
The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'.
</ExceptionMessage>
<ExceptionType>System.InvalidOperationException</ExceptionType>
<StackTrace/>
<InnerException>
<Message>An error has occurred.</Message>
<ExceptionMessage>
Type 'System.Data.Entity.DynamicProxies.Speciality_DC264D6DBBAF52FB19E27F20DCC47DA1141620CEC0CCAF6E2DEF4D8907FA7C8C' with data contract name 'Speciality_DC264D6DBBAF52FB19E27F20DCC47DA1141620CEC0CCAF6E2DEF4D8907FA7C8C:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver if you are using DataContractSerializer or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to the serializer.
</ExceptionMessage>
<ExceptionType>
System.Runtime.Serialization.SerializationException
</ExceptionType>
<StackTrace>
at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiType(XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle objectTypeHandle, Type objectType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle, Type declaredType) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle) at WriteArrayOfSpecialityToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , CollectionDataContract ) at System.Runtime.Serialization.CollectionDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle) at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver) at System.Runtime.Serialization.DataContractSerializer.WriteObject(XmlWriter writer, Object graph) at System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content) at System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken) --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()
</StackTrace>
</InnerException>
</Error>
在我的专业类中没有两个导航属性(Doctors,MedicalFacilities)之前,我没有这个错误。
任何帮助深表感谢。
简要回顾一下-为什么要返回IQueryable
和您的实体模型?
我认为您应该将实体模型转换为仅需要属性的某种DTO,并将动作签名更改为IEnumerable<T>
。
序列化器不知道的是如何序列化EF为您的virtual
属性创建的动态代理。
请在webconfig中输入以下代码段:
var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreservReferencesHandling.Objects;
config.Formatters.Remove(config.Formatters.XmlFormatter);
原因可能是您的导航属性是Interface,所以当您访问服务时它不知道要使用哪种具体类型。 将该列表更改为List看看是否有帮助呢?
使用Serializable()属性。 尝试这个:
namespace Models
{
[Serializable]
public class Speciality
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int SpecialityId { get; set; }
public string Name { get; set; }
public virtual ICollection<Doctor> Doctors { get; set; }
public virtual ICollection<MedicalFacility> MedicalFacilities { get; set; }
}
}
最后,最后起作用的是禁用ProxyCreationEnabled。
所以在我的控制器中,我现在有以下代码:
public class SpecialitiesController : ApiController
{
private ApplicationDbContext db = new ApplicationDbContext();
public SpecialitiesController()
{
db.Configuration.ProxyCreationEnabled = false;
}
// GET: api/Specialities
public IQueryable<Speciality> GetSpeciality()
{
return db.Speciality;
}
}
这确实意味着我将不得不渴望使用.include()加载我要使用的所有导航属性。
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