使用派生类和KnownTypeAttribute时出现SerializationException

Question

我很难获得我的WCF服务来序列化数据合同......当从客户端调用服务时，我得到一个SerializationException，抱怨没有期望我的派生类之一。我在这里发现的所有类似问题都表示修复是使用KnownType和ServiceKnownType，就像我在下面所做的那样，但这对我不起作用。有什么想法吗？

我的服务合同是：

[ServiceContract(...)]
[ServiceKnownType(typeof(DerivedClass))]
public interface IMyService
{
    [OperationContract]
    MainDataClass Process(List<MainDataClass> blah);
}

MainDataClass是：

[DataContract(...)]
[KnownType(typeof(DerivedClass))]
public class MainDataClass
{
    [DataMember]
    public List<BaseClass> Stuff { get; set; }
    ...
}

BaseClass是：

[DataContract(...)]
[KnownType(typeof(DerivedClass))]
public class BaseClass : ICloneable
{
    (lots of [DataMember] properties)
}

DerivedClass是：

[DataContract(...)]
public class DerivedClass : BaseClass
{
    (a few more [DataMember] properties)
}

例外是：

System.Runtime.Serialization.SerializationException
Type 'DerivedClass' 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.
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 WriteArrayOfBaseClassToXml(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.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
at WriteMainDataClassToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , ClassDataContract )
at System.Runtime.Serialization.ClassDataContract.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.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph)