Understanding Project Reunion (Premium)

For the past few years, I’ve hoped that Build would finally provide a bit of clarity for Windows developers. This year, it happened. And I gotta tell you, I feel pretty good about it.

Granted, I’m still struggling to process the firehose of information that Microsoft just sprayed in our collective faces. But that’s a good thing: While Build will continue to be dominated by Azure news, there was plenty of news for those of us more concerned about the client. And not just Windows 10 specifically, but Microsoft Edge and Microsoft 365 too. It was a nice change.

For now, however, I’d like to continue focusing on the Windows app development story and, more specifically, on Project Reunion, Microsoft’s (temporary?) name for this new effort. Yesterday, I wrote my introductory post about this push forward. Today, I’d like to expand on that information by explaining what I’ve learned since then from both Microsoft and my hands-on experiences.

Project Reunion is the new name for a strategy that Microsoft has been working on for years and began quietly hinting at last year at Build 2019. At that time, a certain Microsoft executive who asked for their comments to be off the record started planting the seeds for Reunion by declaring that the Universal Windows Platform (UWP) was “dead” and that the Microsoft Store would be deemphasized going forward.

This year, we have a lot more clarity of both of these moves. And while I won’t focus on the Store story here, the short version is that the Microsoft Store will become a graphical front-end for the new app package manager technology that Microsoft also announced this week.

So, what is Project Reunion really?

Project Reunion is a modern replacement for UWP and a way to use APIs that were previously locked into UWP in other developer frameworks, including Win32/C++, Windows Forms, Windows Presentation Foundation (WPF), and React Native.

There are two Project Reunion components today: WinUI, which provides the UX components previously locked in UWP, and WebView2, which allows developers to embed web technologies in native apps. (WebView1 was based on legacy Edge, while WebView2 is based on the new Edge.) Microsoft says that it will strip more APIs out of UPW and add them as Project Reunion components based on developer feedback.

I can’t imagine that there’s anything else of value in UWP, but whatever: The UX components are excellent, and given that I recently created multiple versions of .NETpad across WinForms, WPF, and UWP, I can state with certainty that the one thing from UWP I do want to use in the other versions of the app is the UX stuff. And I can already see exactly how this will work.

If you’re a developer and want to get started yourself, Microsoft has some instructions here. But the short version is that you need four things: The Visual Studio 2019 Preview (version 16.7 Preview 1), .NET 5.0 Preview 4 x86, .NET Preview 4 x64, and the WinUI 3.0 Pre...