Is there difference in speed between Dictionary.ContainsKey/Value and a foreach loop that checks for a certain key/value

Is there difference in speed between Dictionary.ContainsKey/Valu开发者_如何学Goe and a foreach loop that checks for a certain key/value?

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ContainsKey is faster :

This method approaches an O(1) operation.

ContainsValue is like a foreach loop.

This method performs a linear search; therefore, the average execution time is proportional to Count. That is, this method is an O(n) operation, where n is Count.

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Yes.

ContainsKey is nearly O(1). As for ContainsValue, I can't tell for sure, but I think there won't be much difference to a loop.