There is no harm using LINQ's Count() with a List

It was my understanding and I think others that you should never call LINQ’s Count() extension method on a List because it doesn’t use List’s Count property, resulting in a performance of O(N) instead of O(1).

That’s wrong. LINQ checks if the type is of ICollection, which has the Count property, and returns it if so.

Good to know. I’ve actually always used LINQ’s Count() with lists, and I just assumed there was something in there to give it good performance.

I remember years ago looking up if that was the case and I thought it was determined that it wasn’t smart.