Microsoft's refusal to port WinForms is truly the most disappointing part of its cross-platform efforts, in my opinion. They have Mono, they can get it working, they just choose not to.

I wouldn't build a production application in WinForms, WPF and friends are much better for that. But, for quick&dirty or even moderately complex tools for experts, VS + WinForms simply has no equal. Some Python-based designers come close, but they definitely suffer when it comes to distribution.

With modern dotnet tech, Microsoft could allow us to build a (rather sizable) single, statically linked binary for any architecture, with the impressive performance of the dotnet JIT and native controls.

After working on Android designs, I've got to say, XML is fine for UI design. You need previews and visual inspectors to get an accurate idea of what you're doing, but describing what control lives where and what properties it has is a perfectly sensible use case for XML.

It wouldn’t make much sense to port Winforms any more, as it is CPU-renderer only. It would be disappointingly slow for anything more complex than, well, forms.

XML is actually pretty good at declaring UI. It's the sort of thing the language was designed for - a UI is a tree of attributed nodes, and that's also what XML gives you.

Winforms is undead.

We'll be writing WinForms applications in the 22nd century.