protobuf-net and an empty property in subclass

Question

I was trying to use protobuf-net and faced with the following problem. I have two classes.

[ProtoContract]
class parent
{
    [ProtoMember(1)]
    public string name { get; set; }
}

[ProtoContract]
class child : parent
{
    [ProtoMember(2)]
    public int num { get; set; }
}

If I create a child object without setting the child property "num"

var obj = new child() { name = "tester" };

and try to serialize it

using (var stream = new MemoryStream())
{
    Serializer.NonGeneric.Serialize(stream, obj);
}

the stream will be empty.

Is there any way to handle this situation without using the attribute [ProtoInclude] for the parent class?
I'm using protobuf-net v2 r480.

Thanks

score 1 · Accepted Answer · answered Jul 13 '12 at 17:45

The correct answer here is to use ProtoInclude to tell it about the sub-type. Otherwise, it is only serializing relative to "child", and without any interesting data (zero does not count as interesting by default) a zero-length stream is the correct serialization. Protobuf does not preclude empty streams.

If you can't use ProtoInclude because the type is not known at compile-time, then you can use;

RuntimeTypeModel.Default[typeof(parent)]
    .AddSubType(number, typeof(child));

Note that "number" must be accurately repeatable later on, else it won't deserialize correctly.

protobuf-net and an empty property in subclass

1 Answers1