Why is String.IsNullOrEmpty faster than String.Length?

Question

ILSpy shows that String.IsNullOrEmpty is implemented in terms of String.Length. But then why is String.IsNullOrEmpty(s) faster than

Answer 1

I think it is impossible IsNullOrEmpty to be faster because as all the rest said it also makes a check for null. But faster or not the difference is going to be so small, that this gives a plus on using IsNullOrEmpty just because of this additional null check that makes your code safer.