Build errors when using TFM of 17763

[andrewleader]

Describe the bug
This is a known issue (we need to update the NuGet package dependencies in the Microsoft.ProjectReunion.WinUI NuGet package). Despite Project Reunion supporting down to build 17763 of Windows 10, if you use the .NET TFM of net5.0-windows10.0.17763 or set the packaging project's <TargetPlatformVersion> to 17763 or lower, the project won't build, receiving build errors like Project XYZ is not compatible with uap10.0.17763.

Workaround
Update your TFM to net5.0-windows10.0.18362 or higher, and in your packaging project, update your <TargetPlatformVersion> to 18362 or higher. This will not prevent you from running on 17763 (MinVersion declares that). This only affects what APIs are available (more APIs will be available by targeting a higher version).

Steps to reproduce the behavior:

1. Create a 0.5 or 0.8 Preview WinUI 3 desktop app
2. Change the TFM to net5.0-windows10.0.17763, or change the packaging project's <TargetPlatformVersion> to 17763
3. Try to build the project

Expected behavior
Building and deploying should succeed, since Project Reunion supports down to 17763.

Version Info

NuGet package version:
Version 0.5.7 and 0.8.0-preview

Root cause
The Microsoft.ProjectReunion.WinUI NuGet package declares a dependency on net5.0-windows10.0.18362 or higher, when this instead should be targeting net5.0-windows10.0.17763. Internal bug number 33525703.

[asklar]

@andrewleader how should this work for libraries (as opposed to apps)? we have a winrt library written (in C++) that we are projecting onto C# / reunion via cswinrt, we would like to make the library available to the most number of apps, but when using 17763 we hit this issue.

[andrewleader]

Fixed in upcoming 1.0 Preview 2. You'll now be able to use a TFM of 17763 in apps (or libraries) with WinAppSDK 1.0 Preview 2.