Mark parameters as NOT nullable in C#/.NET?

Question

Is there a simple attribute or data contract that I can assign to a function parameter that prevents null from being passed in C#/.NET? Ideally this would also

Answer 1

I know this is a VERY old question, but this one was missing here:

If you use ReSharper/Rider you may use the Annotated Framework.

Edit: I just got a random -1 for this answer. That's fine. Just be aware it is still valid, even though it's not the recommended approach for C#8.0+ projects anymore (to understand why, see Greg's answer).