PolySharp VS ReferenceAssemblyAnnotator

Great improvements.

There is PolySharp project that enables you to use most of C#11 features in legacy .NET Framework: https://github.com/Sergio0694/PolySharp - Seems that C#12 features are planned to be implemented: https://github.com/Sergio0694/PolySharp/issues/78

I'm using PolySharp where I'm stuck with .NET Framework 4.6 and I don't have any issues.

Hope one day I'd see concise syntax for catch and/or try expressions: https://github.com/dotnet/csharplang/discussions/2734 - but there is a lot of resistance.

You can go one step further and add https://github.com/Sergio0694/PolySharp to your project and you can use new C# 8+ features that don't require the new runtime (like file scoped namesapces, nullable annotations etc).

Is there a reason you're trying to reinvent PolySharp?

You can still use C# 11 (with PolySharp), and you can still get a huge amount of new APIs via the various packages on NuGet that target .NET Standard 2.0. Plus you just get the usual .NET type system and BCL, which are still very good even if when using a framework from a few years ago.

Or the PolySharp NuGet package, which uses source generators to polyfill the language features you're actually using.

Here's some: - MVVM Toolkit - PolySharp - ComputeSharp

Well using PolySharp, of course! 😄

⚠️ Because PolySharp uses source generators, it doesn't work with the package.config file as stated in this issue. The issue says we need to use the SDK style .csproj, but just changing from package.config to Package Reference worked for me.

Some features like records and range require additional boilerplate classes to be added to become usable. You can DIY that or use PolySharp. Some features like static abstract members, default interface methods, etc require runtime support and can't be used.

https://github.com/manuelroemer/Nullable (backport nullable attributes so you can use things like [NotNullWhen]). Alternatively, https://github.com/tunnelvisionlabs/ReferenceAssemblyAnnotator/ is even niftier, as it gives you .NET 5's annotations as well. So the compiler tells you whether a Dictionary.TryGetValue result is nullable or not based on annotations that didn't exist in .NET Standard 2.0.

If you need the attributes, reference https://github.com/manuelroemer/Nullable or https://github.com/tunnelvisionlabs/ReferenceAssemblyAnnotator. The latter is bigger, but retroactively adds nullability annotations to runtime references (such as Dictionary.TryGetValue).

EDIT: A reader reached me about this cool package that partially solves this problem by injecting nullable reference type annotations in CLR's methods of some assemblies (check the docs for more details): ReferenceAssemblyAnnotator.

This helps: https://github.com/tunnelvisionlabs/ReferenceAssemblyAnnotator

Can't use 6.0 on that solution because https://github.com/tunnelvisionlabs/ReferenceAssemblyAnnotator/issues/89. But I did try 6.0 on a smaller project, where indeed, the warning seems to only appear if I downgrade to the 5.0.400 SDK. With 6.0.400, I get… a build error instead. With that workaround, it works.

https://github.com/tunnelvisionlabs/ReferenceAssemblyAnnotator to get Nullable Reference Type annotations from .NET 5 backported to Fx