Is there a difference between Dictionary.Keys.Contains (key) and Dictionary.ContainsKey (key)

Question

Let's pretend that:

Dictionary<Guid, MyClass> dict;

Is there any difference between

dict.Keys.Contains(key)

and

dict.ContainsKey(key)

I thought there was no difference, but now I'm not sure.

Answer 1

These two methods are guaranteed to return the same value of true/ false.

According to the reference implementation , dict.Keys.Contains(key)delegates dict.ContainsKey(key):

bool ICollection<TKey>.Contains(TKey item){
    return dictionary.ContainsKey(item);
}

This method is part of the class KeyCollection. Its field dictionaryrefers to the object dictionaryto which KeyCollectionit returned the property Keys.

Answer 2

, , .

Dictionary.Keys . , , .

, .

Answer 3

.

dict.ContainsKey(key) .

dict.Keys.Contains(key), . IEnumerable<TKey>, () . , , .