ProtoBuf.net Base class properties is not included when serializing derived class

Question

Using latest 2.0 beta version of ProtoBuf.net I am trying to serialize derived class(just example) and I get empty file. Why base class properties is not serialized?

[ProtoContract]
[Serializable]
public class Web2PdfClient : Web2PdfEntity
{

}

[ProtoContract]
[Serializable]
public class Web2PdfEntity : EngineEntity
{

    [ProtoMember(1)]
    public string Title { get; set; }
    [ProtoMember(2)]
    public string CUrl { get; set; }
    [ProtoMember(3)]
    public string FileName { get; set; }

}


[ProtoContract]
[Serializable]
public class EngineEntity
{

    public bool Result { get; set; }
    public string ErrorMessage { get; set; }
    public bool IsMembershipActive { get; set; }
    public int ConversionTimeout { get; set; }
    public byte[] FileStorage { get; set; }
}

While using code below to serialize class I get empty file.

var Web2PDF = new Web2PdfClient
                          {                                
                              CUrl = "http://www.google.com",
                              FileName = "test.txt"
                          };
        using (var file = File.Create(@"C:\Users\Administrator\Projects\temp\test.bin"))
        {
            Serializer.Serialize(file, Web2PDF);

        }

Answer 1

Actually, I'm quite surprised that didn't throw an exception - I will investigate! In order for that to work, the base-type must have a unique way to indicate each of the sub-types. This can be specified via attributes, or (in v2) at runtime. For example:

[ProtoContract]
[Serializable]
public class Web2PdfClient : Web2PdfEntity
{

}

[ProtoContract]
[ProtoInclude(7, typeof(Web2PdfClient))]
[Serializable]
public class Web2PdfEntity : EngineEntity
{ ... }

There's nothing special about 7 except that it shouldn't collide with any other members defined for that type. Multiple subtypes can be defined (with different tags). Note also that protobuf-net doesn't look at [Serializable], so you don't need that unless you are also using BinaryFormatter (or similar).

Similarly, EngineEntity should advertise its expected subtypes, and should indicate the members to serialize (and against which tag).