[aaronbrethorst]

Parts of VS may have a WPF UI, but I can assure you the vast majority of the codebase is C++.

[Encosia]

When no dialogs are open, the overwhelming majority of the UI is WPF now though, to my knowledge. I remember running debug builds of 2010 that showed paint rectangles and there was basically nothing that wasn't WPF even in that first WPF version.