Fix an issue when using classes with similar APIs.

[matthid]

When you use Exposed on similar APIs you will run into issues as the DLR will cache requests and fail (or even worse return wrong results)

[skolima]

Hi @matthid , this looks like a really well prepared PR! Thank you very much. I'll do my best to check it in detail soon.

[skolima]

Hey. I gave this a go, unfortunately it doesn't include the code path for versions without nullable annotation support. I could bump the library to be only netstandard2.0 and net6.0 (like e.g. NodaTime is now) and see what approach Skeet takes to make this work (I though nullable annotations don't work at all on netstandard). I'll be back after bumping the targets...

[matthid]

Yes I was a bit confused what was going on there. I thought Nullable is a compiler feature, and you can increase the compiler version to latest https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version and just enable nullable (even for old net framework). This way you should be able to get rid of the compiler directive. I'm not sure if this public-api check you have in place supports that though.

[skolima]

I've dropped the older targets and the path without nullable annotations from the main branch, but I'm now having issues merging this back into your branch. I keep getting NPEs when testing static members. Could you have a got with updating your branch from my main please?