Tfm support build warnings question

[westin-m]

I am trying to understand the build warning I am seeing for a couple different Extensions packages, e.g. "Microsoft.Extensions.Telemetry 9.0.0 doesn't support net48 and has not been tested with it." I have read the response in #4952 and hope to get more/different information. What does it mean that the packages are not tested, and what are the risks of using these packages in .NET Framework?

Just in case it makes a difference, the packages we see the warning for are AmbientMetadata.Application, Compliance.Redaction, DependencyInjection.AutoActivation, Telemetry, and Telemetry.Abstractions.

[mohammadhoseindehghani]

I think there is an important distinction between a package being technically compatible with .NET Framework and being officially supported on it.

In some cases, the package may contain binaries that can run on .NET Framework 4.8, but that doesn't necessarily mean the maintainers test or guarantee that configuration.

The warning is basically telling you that you're using the package outside its supported target frameworks. It doesn't automatically mean the package will fail at runtime, but you shouldn't assume that everything will work just because the project builds successfully.

Some possible risks are:

• Runtime issues caused by APIs or dependencies that behave differently on .NET Framework.
• Bugs in code paths that aren't covered by tests for net48.
• Future package updates introducing changes that haven't been validated against .NET Framework.

I would check the target frameworks listed in each package on NuGet and, more importantly, the package's official support policy.

There was also a related discussion in this repository (#4952), where a maintainer clarified that some Microsoft.Extensions packages may have binaries compatible with .NET Framework 4.6.2+, but that doesn't mean .NET Framework is an officially supported target.

If you have to keep using these packages in a net48 application, I'd recommend pinning the package versions and running integration tests against the actual .NET Framework runtime, rather than relying only on a successful build.

Suppressing the warning is possible, but it only hides the warning. It doesn't make the configuration supported.