I have two ICollections of which I would like to take the union. Currently, I'm doing this with a foreach loop, but that feels verbose and hideous. What is the C# equivalent of Java's addAll()?

Example of this problem:

            ICollection<IDictionary<string, string>> result = new HashSet<IDictionary<string, string>>();
            // ...
            ICollection<IDictionary<string, string>> fromSubTree = GetAllTypeWithin(elementName, element);
            foreach (IDictionary<string, string> dict in fromSubTree) // hacky
            {
                result.Add(dict);
            }
            // result is now the union of the two sets