But some of the callers is the Dictionary's TryGetValue and ContainsKey and so require the result of the method to be a Dictionary, how can I convert the IEnumerable into a Dictionary so that I can use TryGetValue ? I've a method which at present returns an IEnumerable. I want to make it more generic by making it return an IEnumerable. method: public IEnumerable<KeyValuePair<string, ArrayList>> GetComponents() { // ... yield return new KeyValuePair<string, ArrayList>(t.Name, controlInformation); } caller: Dictionary<string, ArrayList> actual = target.GetComponents(); actual.ContainsKey("something");