Small tweaks

[Corniel]

Well inspecting the code, I found 3 minimal code changes that make the code easier to read and potentially (a tiny bit) faster:

The first reduces the numbers of dictionary look ups, and the others involves casting to IValdatebleObject and IAsyncValdatebleObject. The latter technique could also be applied to IENumerable but than the nested path building has to change, and that might be worth another PR.