Are LINQ .Last, .Skip, etc. methods optimized for arrays or List<T>?

I'm wondering if LINQ methods like .Last and .Skip are optimized for arrays, List<T> and such. E.g. for an array I could do _array[_array.Length - 1] to get the last element.开发者_如何学Python Does _array.Last() actually enumerate through all elements and then return the last or is there actually some optimization built in?

Might have to forgo fluency for performance if not.

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Last() is optimized when there isn't a predicate... it could be optimized even if there is a predicate (by working back from the end), but it isn't.

I don't think Skip is optimized - although again, it could be.

Basically most of LINQ to Objects is optimized where it can be (for ICollection<T>, ICollection, and IList<T>) but there's still room for more to come.