IsExternalInit VS MSBuild.SDK.SystemWeb

You can also just reference the https://github.com/manuelroemer/IsExternalInit NuGet package.

init only properties (likely to come up if you use records) - you can either use the IsExternalInit nuget package or manually define the attributes - either way, the feature works perfectly fine

…and a NuGet reference to https://www.nuget.org/packages/IsExternalInit, I can then do public record Foo(string s); and have it build.

You only need https://github.com/manuelroemer/IsExternalInit for that (and to set LangVersion).

Even for .NET Framework code, I tend to use recent C# versions. I reference https://github.com/jnm2/ReferenceAssemblyAnnotator to get nullable support and https://github.com/manuelroemer/IsExternalInit for records, and that takes care of most of the features I care about.

features that require BCL additions. Since you're on the older BCL, those will need to be backported. For example, to use init; and record, you can use https://github.com/manuelroemer/IsExternalInit.

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.