Do collections that prevent inserting the duplicate elements work slower?

Do collections that prevent inserting the dupl开发者_如何学Goicate elements work slower(than the non-checking ones), as I guess they implement some kind of check on each element within against duplication?

Or it is not correct or tolerable in most of the cases?

Thanks

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It depends on the implementation of course, but most sets are likely to be optimised in some form to check for containment quickly. For example, HashSet<T> is basically a hash table of values - so it's just a hash lookup.

I don't know of any collections which would check every existing element for equality (unless you have a horrible hash collision situation etc).

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That totally depends on the implementation of the collection you are using - if it is based on a List<T> there will be a performance penalty.

However, if a HashSet<T> is used, the performance will be almost the same.

Still, performance shouldn't be the motivation here. If you want to allow duplicate items, use a list that does, otherwise use one that doesn't.