MSBuild.SDK.SystemWeb VS Nullable

I have some projects stuck on that, but not a lot. For web stuff, https://github.com/CZEMacLeod/MSBuild.SDK.SystemWeb does most of the heavy lifting, although things like publishing are broken.

I’ve had great luck with this on older ASP.NET projects https://github.com/CZEMacLeod/MSBuild.SDK.SystemWeb

You can use this unofficial project to modernize your .NET Framework project and take advantage of things like PackageReferences.

Sdk at least works with .net standard so shared projects can be converted to that, we also had some success using the MSBuild.SDK.SystemWeb sdk nuget package for our MVC5 projects which I found from the github issue discussions on adding official support for it on older projects.

I've been a bit luckier in that regard, but I'm not sure if your path wouldn't have taken less effort. I use https://github.com/hvanbakel/CsprojToVs2017 (dotnet migrate-2019 wizard) to modernize the projects, then further tweak them by hand. For ASP.NET projects, it's indeed a very difficult road. WebForms outright doesn't exist, and Core is very different from MVC in some areas. https://github.com/CZEMacLeod/MSBuild.SDK.SystemWeb helps somewhat.

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).