Is not WinUI the extraction of the UI part of the UWP stack? Yes namespaces break, but concepts and controls are from the same linage. UWP is more than the UI. It has also sandboxing and deployment.
So essentially, it is not a new UI. Just a new version of an old one.
(consider e.g. WinForms was also ported from .NET Framework to .NET Core. That is also not counted here ;))
So essentially, it is not a new UI. Just a new version of an old one.
(consider e.g. WinForms was also ported from .NET Framework to .NET Core. That is also not counted here ;))