Add .net standard 1.4 target to Microsoft.Toolkit project.

[matthew4850]

PR Type

What kind of change does this PR introduce?

• Add support to older .net standard versions

What is the new behavior?

The Microsoft.Toolkit project may now be used in .net standard 1.4 projects.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

[ghost]

Thanks matthew4850 for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

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[Sergio0694]

Left a few suggested changes, once those are accepted the rest looks good to me! 🚀

[ghost]

This PR has been marked as "needs attention 👋" and awaiting a response from the team.

[michael-hawker]

@Sergio0694 @azchohfi can you help me understand the ramifications here? It shouldn't make a difference to anyone using a newer engine version like UWP 16299+ or .NET Core 3, eh?

What happens in the future if we want to add an API that's only supported on 2.0+, then we'd have to box it in an ifdef and it'd be left out of the package for anyone on 1.4??

[azchohfi]

Yes, that is exactly it.
I wonder why @matthew4850 wants this. 1.4 is very old.
https://docs.microsoft.com/en-us/dotnet/standard/net-standard
Is it for older UWP target (10.0) support?

[Sergio0694]

@azchohfi Yup, Matthew is still targeting Windows 10 Mobile in his app (yeah, he's a mad lad), so he's locked to .NET Standard 1.4, as mobile is stuck on Windows 10 build 15063 😆

@michael-hawker Yeah, as Alex said it makes absolutely no difference for newer platforms. NuGet will automatically pick the closest possible match for the current platform when installing the package.

[michael-hawker]

@azchohfi I think the motivation here is (as @Sergio0694 said) is that we don't explicitly use anything unique to .NET Standard 2.0, so we can target the lowest denominator for now to have broader reach.

Should we take this for 6.1?

[Sergio0694]

@michael-hawker The new HighPerformance package supports extensive multi-target as well (including .NET Standard 1.4), so especially considering how small this PR is, and the fact that it's not breaking anything, I guess it should be fine to include this in 6.1 if you want 👍

[ghost]

This PR has been marked as "needs attention 👋" and awaiting a response from the team.

[azchohfi]

I'm ok merging this for 7.0. @michael-hawker ?

[Sergio0694]

The PR is valid and @matthew4850 had already done a couple tweaks I had suggested, so this is good to go for me. Just as a note though, the original interest was to be able to use the base package on Windows 10 Mobile (so W10 with SDK < 16299), which lacks support for .NET Standard 2.0. This will still not work due to a known .NET Native issue there (lack of support for Span<T> APIs which causes a build failure as soon as you add a reference to System.Memory.

So the package itself will still not work on Windows 10 Mobile, if that matters.
The PR itself though is perfectly valid on its own 👍

[Sergio0694]

This PR is good to go (up to date, reviewed with two approvals, etc.), and the CI is passing as well.
Just holding off on this for @michael-hawker to confirm this is fine to merge (see question from @alexchx here) 👍

[michael-hawker]

Let's test this out and see how all the multi-targeting stuff goes. Worse case if we need a new feature and it gets messy we bump back up in the future.

Thanks for the contribution @matthew4850 and pushing the bounds of the Toolkit! 🎉