Performance difference between .where(…).Any() vs ..Any(…) [duplicate]

Answer 1

I believe this is due to the Where enumerating all items.

If myList is a collection in memory, it doesn't. The Where method uses deferred execution, so it will only enumerate as many items as needed to determine the result. In that case you would not see any significant difference between .Any(...) and .Where(...).Any().

Are there any cases where this viewed performance difference wouldn't be the case, like if it was querying Nhib?

Yes, if myList is a data source that will take the expression generated by the methods and translate to a query to run elsewhere (e.g. LINQ To SQL), you may see a difference. The code that translates the expression simply does a better job at translating one of the expressions.