Is there any difference between Dictionary.Keys.Contains(key) and Dictionary.ContainsKey(key) [duplicate]

Question

Suppose:

Dictionary<Guid, MyClass> dict;

Is there any difference between

dict.Keys.Contains(key)

and

dict.ContainsKey(key)

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

Answer 1

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

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

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

This method is part of KeyCollection class. Its dictionary field refers to the Dictionary object that owns the KeyCollection returned by Keys property.