Can I add a reference to a .NET Framework DLL from a .NET 5 project?

Question

Microsoft recently announced at Build 2019 that the next major version of .NET will unify both .NET Core 3.* and .NET Framework 4.* into a single .NET platform, which the ma

Answer 1

It will be the same as today: you will be able to reference .NET Standard libraries. .NET 5 does not contain everything of the classic framework, therefore it won't be possible to reference a .NET 4.x assembly directly. Therefore start to write libraries in .NET Standard.

However in .NET Core 2.0 Microsoft implemented the compatibility shim that allows type forwarding of missing tpyes in old assemblies to the new type. As long as your library does not use any classes that are not supported by .NET 5, you're safe.

See this post or this for more information.