protobuf-net v2 type meta

Question

According to this post (from March), protobuf v2 allows us to resolve types from a stream. Since v2 is now in beta 5, I think this feature has already been implemented, so I

Answer 1

The trick here is to use the DynamicType = true option on a member to your object - as an over-simplified example:

[ProtoMember(12, DynamicType = true)]
public object CouldBeAnything {get;set;}

Re the "string<===>Type map", that is the DynamicTypeFormatting event on TypeModel. If you are using the Serializer.* methods, that is a shortcut (mainly for preserving the v1 API) to the RuntimeTypeModel.Default serializer instance.

(as a side-note, in writing this I did notice an edge-case that I need to go and fix in the code)

Note: another approach here, rather than using DynamicType, is to simply configure the model at runtime, for example:

var knownTypes = GetMyKnownTypesAtRuntimeWithUniqueIdentifiers();
var metaType = typeModel[typeof(MyBaseClass)];
foreach(var knownType in knownTypes)
{
    metaType.AddSubType(knownType.UniqueIdentifier, knownType.Type);
}

IMO this latter is my preferred option, and will generally be more efficient. Note that it is necessary for the unique-identifiers to be fixed/repeatable, as that is part of the wire format (don't just use the index of the order you find them).