Adding .NET Standard libraries to 4.7.1 lib adds loads of references, some broken

Question

As I need to import a library targeting .NET Standard 2, I had upgraded my library to .NET 4.7.1, as I understood from this MS video that should avoid this issue: https://www.youtube.com/watch?v=u67Eu_IgEMs

However, adding .NET standard now results in dozens of System.xxx references, rather than a single reference to .NET Standard (as per the video).

Worse still, several of the references have been added but the underlying file appears to be missing generating warnings, e.g. Warning The referenced component 'Microsoft.Win32.Primitives' could not be found. Warning The referenced component 'System.IO.FileSystem' could not be found. Warning The referenced component 'System.Security.Cryptography.X509Certificates' could not be found. Warning The referenced component 'System.Globalization.Calendars' could not be found.
Warning The referenced component 'System.Security.Cryptography.Encoding' could not be found. Warning The referenced component 'System.Security.Cryptography.Primitives' could not be found. Warning The referenced component 'System.IO.Compression.ZipFile' could not be found. Warning The referenced component 'System.Console' could not be found. I even re-created the demo project in video and got the same result - no single reference to .NET Standard, lots of DLL references instead.

I've tried a NUGET update-package -reinstall and downgraded and upgraded to .NET standard 2.0 and 2.0.1 as well

Answer 1

The answer I'm creating for my own question is:

Does your .NET Framework project use packages.config ? If it does, DO NOT reference .NET Standard libraries. The package/reference/binding-redirect in VS 2017 is horribly broken if you introduce .NET Standard. Trying to fix it will cause more problems (I've wasted several days trying). Expect to have assemblies which don't load despite being present, lots of warnings and a broken app.

If you use System.Net.Http, plan on spending several days in Google and GitHub issues trying to get that to work.

If you are able to upgrade to packageReferences, this should fix the problem. But if your project contains packages that import content, like JQuery or Bootstrap be aware that these no longer work and you'll instead spend more time trying to fix those references and migrate to npm or bower, along with fixing TypeScript compilation too. No thanks.

Ideally you'd be using the 2017 csproj format but that's not compatible with WinForms, ASP.NET or Windows Services - so tough if you've got a legacy project.