protobuf-net 序列化所需的已定义 proto2 消息类型？

Question

protobuf-net v2.1.0 ( latest available as NuGet package ) 
Visual Studio 2015 v14 
C#

I'm not using protogen.exe to generate my classes from message-type defs

Because I have additional requirements, I wrote my own generator which writes classes such as :

[Serializable]  
public partial class MyType: ProtoBuf.IExtensible                                   
{                                                                                               
  [ProtoBuf.ProtoMember(1, IsRequired = false, Name = @"RegistrationDate", DataFormat = ProtoBuf.DataFormat.Default)]
  [System.ComponentModel.DefaultValue("1/1/0001 12:00:00 AM")]                                                          
  public DateTime RegistrationDate;                                                                         

  [ProtoBuf.ProtoMember(2, IsRequired = false, Name = @"RegistrationId", DataFormat = ProtoBuf.DataFormat.TwosComplement)]
  [System.ComponentModel.DefaultValue(null)]                                            
  public long? RegistrationId;

But when I attempt to serialize :

var  myObject = new MyType(RegistrationDate="2016-01-01",RegistrationId=1);
var stream = new MemoryStream();
ProtoBuf.Serializer.Serialize(stream, myObject );

protobuf-net throws exception :

An exception of type 'System.InvalidOperationException' occurred in protobuf-net.dll but was not handled in user code

Additional information: Type is not expected, and no contract can be inferred: MyNamespace.MyType

Apparently protobuf-net is expecting the class declaration to be decorated with a proto contract attribute :

[Serializable]
[ProtoBuf.ProtoContract(Name=@"MyTypeProto")]   
public partial class MyType: ProtoBuf.IExtensible                                   
{

However since I'm using types such as DateTime and int? I don't believe it's possible for me to create a compatible proto2 message-type.

How to structure my classes so that protobuf-net can successfully serialize ?

UPDATE : If I add the [Protobuf.ProtoContract] attribute then I can serialize/deserialize with no exceptions thrown, but my deserialized object has lost all values ( all fields are null ) :

[Serializable]  
[Protobuf.ProtoContract]
public partial class MyType: ProtoBuf.IExtensible                                   
{                                                                                               
  [ProtoBuf.ProtoMember(1, IsRequired = false, Name = @"RegistrationDate", DataFormat = ProtoBuf.DataFormat.Default)]
  [System.ComponentModel.DefaultValue("1/1/0001 12:00:00 AM")]                                                          
  public DateTime RegistrationDate;                                                                         

  [ProtoBuf.ProtoMember(2, IsRequired = false, Name = @"RegistrationId", DataFormat = ProtoBuf.DataFormat.TwosComplement)]
  [System.ComponentModel.DefaultValue(null)]                                            
  public long? RegistrationId;

  var  myObject = new MyType(RegistrationDate="2016-01-01",RegistrationId=1);
  var stream = new MemoryStream();
  ProtoBuf.Serializer.Serialize(stream, myObject );
  var deserialized = ProtoBuf.Serializer.Deserialize<MyType>(stream);
  // deserialized.RegistrationDate is null
  // deserialized.RegistrationId is null

Answer 1

All it is asking for is for you to tell it that your type really is intended for protobuf serialization; so:

[ProtoBuf.ProtoContract]   
public partial class MyType ...

The name is entirely optional. Indeed, most uses of protobuf-net are code-first rather than schema-first (or even schema-ever), so I would wager that it is unusual to have an explicit name.

As a side note, though; DateTime and int? can both be expressed in .proto (although the int? is a lot cleaner than the DateTime - it just becomes an optional field, if you choose to generate the schema from the type model, which you don't need to).

It doesn't acknowledge [Serializable] because that means something quite different and isn't even available on all platforms.