Question

I receive a message using protobuf-net. The message has 1 field with the type of the message stored in it (the field is of enum type). Now I know the message is of a type that inherit from the base type. How can I cast the object I get from the Serializer to the appriopriate type?

Definition of classes:

[ProtoContract]
class Annoucement
    {
        public enum msgType
        {
            AKCJA = 0,
            CZEKAJ = 1,
            GOTOWY = 2,
            NOWY_GRACZ = 3,
            LISTA_GRACZY = 4,
            ERROR = 5,
            MAPA = 6,
            UPDATE = 7,
            LISTAGIER = 8,
            JOINGAME = 9,
            QUIT = 10
        }
        [ProtoMember(1)]
        public msgType typ;
    }

[ProtoContract, ProtoInclude(14, typeof(Annoucement))]
    class Update : Annoucement
    {
        [ProtoMember(1)]
        public List<Tank> czolg;
        [ProtoMember(2)]
        public List<Pocisk> pocisk;
        [ProtoMember(3, IsRequired = false)]
        public List<Bonus> bonus;
    }

How can I do something in idea similiar to this:

Annoucement ann = Serializer.DeserializeWithLengthPrefix<Annoucement> (str, PrefixStyle.Base128);
switch (ann.typ) {
case Annoucement.msgType.UPDATE:

                {
                    Update temp = (Update)ann;
                    Console.WriteLine (temp.czolg.Count);
                    List<Tank>.Enumerator i = temp.czolg.GetEnumerator ();
                    Console.WriteLine (i.Current.life);
                }


                break;

Answer 1

It should just work; I believe the problem is that the attributes are inverted (I will take a note to raise a clearer error in this case) – it should be :

[ProtoContract, ProtoInclude(14, typeof(Update))]
class Annoucement
{

}

[ProtoContract]
class Update : Announcement
{

}

i.e. the base needs to know about the descendants. Not I removed the discriminator from serialization, as that is redundant if it relates directly to the object type – it handles this internally via the ProtoInclude and will create the correct type for you. Each type needs to know only about the direct subtypes, i.e.

A
- B
 - C
- D
 - E
 - F

here A needs to know about B and D; B needs to know about C; D needs to know about E and F.

Note that a “what is this” enum is a good idea here, but there is no need for it to be a field – a virtual property without a field may be more appropriate. If I have misundersood and the message-type doesn’t relate to the object-type, then ignore me ;p

Also: public fields – don’t do it. Think of the kittens… It will work, but properties are preferred (in general, I mean; nothing to do with protobuf-net).