`Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll` is included in output of framework-dependent unpackaged app

[sylveon]

Describe the bug

Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll is copied to the publish output of unpackaged apps, despite not being relevant (it only applies to packaged apps).

Steps to reproduce the bug

1. Create a new C# app using the WinUI Blank App (Packaged) template
2. Add <WindowsPackageType>None</WindowsPackageType> to the csproj
3. (optional) Enable NAOT by also adding <PublishAot>true</PublishAot> and upgrading the target framework to .NET 9 (this removes a lot of stuff from the output, making the issue more apparent)
4. Set the build configuration to Release in VS
5. In the solution explorer, right click on the project and hit publish. Then in the window that opens, hit publish, and once it finishes, hit navigate to open the published directory
6. Observe the presence of Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll

Expected behavior

This DLL should not be present

Screenshots

NuGet package version

Windows App SDK 1.7.1: 1.7.250401001

Packaging type

Unpackaged

Windows version

Windows 11 version 24H2 (22621, October 2024 Update)

IDE

Visual Studio 2022-preview

Additional context

No response

[godlytalias]

This happens as the SelfContained need to be set to true while publishing for C# apps. @manodasanW / @Scottj1s Any guidance here to avoid a specific DLL in case of C# apps?

In case of C++ apps this gets handled using WindowsAppSDKBackgroundTask property in the project file

[Scottj1s]

The title is a bit confusing. PublishAot implies SelfContained (not framework-dependent). In any case, I'd suggest following the pattern adopted by WebView2, which explicitly references assemblies/winmds to discriminate between WPF and WinUI3 (WinAppSDK) scenarios, vs relying on automatic referencing via TFM. Use additional conditions to appropriately default WindowsAppSDKBackgroundTask, such as '$(WindowsPackageType)'!='None'. Use binlogs and http://msbuildlog.com to debug.

[sylveon]

PublishAot is .NET self-contained, but WASDK framework dependent. The issue also reproduces with a .NET framework dependent trimmed publish. I just used NAOT to highlight the issue, as there is less DLLs in the output of a NAOT app.