Question

I assume it looks at your model and somehow gets things ready, so that your first few serializations aren’t slowed. What if my messaging model has a message class with child classes? Does putting my parent class in the type argument prepare all the children too?

Answer 1

(this answer assumes protobuf-net v2)

If you mean Serializer.PrepareSerializer<T>(), then it will certainly inspect all the child-types, so the type-model will be prepared for them (meaning: it will figure out what fields/properties etc need serializing). It will pre-compile (i.e. IL-emit) the code for the parent class, but (looking at the code) not specifically for the derived types. If unattended, the derived types will compile themselves when first needed. I think! I can do a thorough check if you really want.

However, if you use RuntimeTypeModel.Default.CompileInPlace(), it builds the entire model – everything known is prepared. Of course, that then leaves the dilemma of having to tell the model about them first ;p

I’ll double check to see at what point the sub-type serializers are prepared, just to be sure. It might indeed make sense to cascade them.

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Update:

it looks like it does indeed cascade to derived types, but not to the parent type (if any):

    [Test]
    public void CheckTypeSpecificCompileInPlaceCascadesToBaseAndChildTypes()
    {
        var model = TypeModel.Create();
        model[typeof(B)].CompileInPlace();

        Assert.IsTrue(model.IsPrepared(typeof(D)), "D"); // sub-sub-type
        Assert.IsTrue(model.IsPrepared(typeof(C)), "C"); // sub-type
        Assert.IsTrue(model.IsPrepared(typeof(B)), "B"); // self
        Assert.IsTrue(model.IsPrepared(typeof(A)), "A"); // base-type
    }

    [Test]
    public void CheckGlobalCompileInPlaceCascadesToBaseAndChildTypes()
    {
        var model = TypeModel.Create();
        model.Add(typeof (B), true); // give the model a clue!
        model.CompileInPlace();

        Assert.IsTrue(model.IsPrepared(typeof(D)), "D"); // sub-sub-type
        Assert.IsTrue(model.IsPrepared(typeof(C)), "C"); // sub-type
        Assert.IsTrue(model.IsPrepared(typeof(B)), "B"); // self
        Assert.IsTrue(model.IsPrepared(typeof(A)), "A"); // base-type
    }

Here, the second test passes; the first test fails citing “A” – so the sub-types (“C” and “D”) were fully compiled. Since the base type will still get compiled on demand, this is probably fine as-is, but I could probably make it tract to ancestor types if that would be useful.

(the IsPrepared method only exists in my local copy)