Map a class in XAML that isn't in a namespace

Question

Yes I know this is considered bad practice, and for the most part I actually agree (i.e. no need to debate that point) but I'm wondering if it's possible to reference in XAML classes that aren't contained within a namespace. In other words, root-level classes.

Again, I know this is bad practice, but I am curious.

(BTW, yes I know about mapping namespaces to the URI Microsoft uses at the assembly level so you can type the classes without namespace prefixes in XAML, but technically those classes are still in a namespace so that's not what I'm referring to.)