protobuf -net doesn’t know how to serialize datamember that are of type = object

Question

We have the following class as part of an ADO.NET Provider running over the wire using WCF.

[KnownType(typeof(AdoServiceCommandExecutionScalarResult))]
[DataContract(Namespace = Namespaces.SoafXmlNamespace)]
public class AdoServiceCommandExecutionResult
{
}
[DataContract(Namespace = Namespaces.SoafXmlNamespace)]
public class AdoServiceCommandExecutionScalarResult : AdoServiceCommandExecutionResult
{
    [DataMember]
    public object Result { get; set; }

    public override string ToString()
    {
        return new XDocument(new XElement(GetType().Name, new XAttribute("Result", Result))).ToString();
    }
}

We are trying to use protobuf-net for serialization however there is an exception thrown that the type object cannot be resolved.

Exception Message:

No serializer defined for type: System.Object

Stack Track:

ProtoBuf.Meta.ValueMember.BuildSerializer()
ProtoBuf.Meta.ValueMember.get_Serializer()
ProtoBuf.Meta.MetaType.BuildSerializer()
ProtoBuf.Meta.MetaType.get_Serializer()
ProtoBuf.Meta.MetaType.ProtoBuf.Serializers.ISerializerProxy.get_Serializer()
ProtoBuf.Serializers.SubItemSerializer.ProtoBuf.Serializers.IProtoTypeSerializer.HasCallbacks(CallbackType callbackType)
ProtoBuf.Serializers.TypeSerializer.HasCallbacks(CallbackType callbackType)
ProtoBuf.Serializers.TypeSerializer.ProtoBuf.Serializers.IProtoSerializer.EmitWrite(CompilerContext ctx, Local valueFrom)
ProtoBuf.Compiler.CompilerContext.WriteNullCheckedTail(Type type, IProtoSerializer tail, Local valueFrom)
ProtoBuf.Compiler.CompilerContext.BuildSerializer(IProtoSerializer head, TypeModel model)
ProtoBuf.Serializers.CompiledSerializer..ctor(IProtoTypeSerializer head, TypeModel model)
ProtoBuf.Meta.MetaType.get_Serializer()
ProtoBuf.Meta.RuntimeTypeModel.Serialize(Int32 key, Object value, ProtoWriter dest)
ProtoBuf.Meta.TypeModel.TrySerializeAuxiliaryType(ProtoWriter writer, Type type, DataFormat format, Int32 tag, Object value, Boolean isInsideList)
ProtoBuf.Meta.TypeModel.TrySerializeAuxiliaryType(ProtoWriter writer, Type type, DataFormat format, Int32 tag, Object value, Boolean isInsideList)
ProtoBuf.Meta.TypeModel.SerializeCore(ProtoWriter writer, Object value)
ProtoBuf.Meta.TypeModel.Serialize(Stream dest, Object value, SerializationContext context)
ProtoBuf.ServiceModel.XmlProtoSerializer.WriteObjectContent(XmlDictionaryWriter writer, Object graph)
System.Runtime.Serialization.XmlObjectSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph)
System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
System.Runtime.Serialization.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph)
System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameterPart(XmlDictionaryWriter writer, PartInfo part, Object graph)
System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeParameter(XmlDictionaryWriter writer, PartInfo part, Object graph)
System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter.SerializeBody(XmlDictionaryWriter writer, MessageVersion version, String action, MessageDescription messageDescription, Object returnValue, Object[] parameters, Boolean isRequest)
System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer)
System.ServiceModel.Channels.Message.OnWriteMessage(XmlDictionaryWriter writer)
System.ServiceModel.Channels.BufferedMessageWriter.WriteMessage(Message message, BufferManager bufferManager, Int32 initialOffset, Int32 maxSizeQuota)
System.ServiceModel.Channels.TextMessageEncoderFactory.TextMessageEncoder.WriteMessage(Message message, Int32 maxMessageSize, BufferManager bufferManager, Int32 messageOffset)
System.ServiceModel.Channels.HttpOutput.SerializeBufferedMessage(Message message)
System.ServiceModel.Channels.HttpOutput.Send(TimeSpan timeout)
System.ServiceModel.Channels.HttpPipeline.EmptyHttpPipeline.SendReplyCore(Message message, TimeSpan timeout)
System.ServiceModel.Channels.HttpRequestContext.OnReply(Message message, TimeSpan timeout)
System.ServiceModel.Channels.RequestContextBase.Reply(Message message, TimeSpan timeout)
System.ServiceModel.Channels.RequestContextBase.Reply(Message message, TimeSpan timeout)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.Reply(MessageRpc& rpc)

Is it possible to resolve this?

EDIT: We have a custom routine that basically does (simplified for brevity).

type.GetAttributes<KnownTypeAttribute>().Select(a => a.Type).Distinct().ForEach(t => AddKnownTypeHierarchy(t));  

public static void AddKnownTypeHierarchy(Type type)
{

    ProtoBuf.Meta.MetaType metaType = RuntimeTypeModel.Default.Add(type, true);
    ...
    var fieldNumber = derivedType.MetadataToken;
    metaType.AddSubType(fieldNumber, derivedType);
    ...
    var memberType = member.MemberInfo.As<PropertyInfo>().IfNotNull(p => p.PropertyType) ?? member.As<FieldInfo>().IfNotNull(f => f.FieldType);
    var field = metaType.AddField(member.Order, member.Name);
    if (memberType == typeof (object) || memberType.EqualsGenericTypeFor(typeof (IEnumerable<>))) field.DynamicType = true;
    ...
}

We adding logic that if an object is encountered that it should be treated as dynamic. That approach resulted in the following exception:

Dynamic type is not a contract-type: Int32

Is it possible to add support for treating object as dynamic instead?

Answer 1

Protobuf requires a specific type to serialise/deserialise. you will need to give it something specific rather than Object.