public void CanDiff()
        {
            DictionarySet <string> set1 = new DictionarySet <string>();

            set1.Add("a");
            set1.Add("b");
            set1.Add("c");

            DictionarySet <string> set2 = new DictionarySet <string>();

            set2.Add("b");
            set2.Add("d");
            set2.Add("e");

            ComLib.Collections.ISet <string> diff = set1.Minus(set2);
            Assert.IsFalse(diff.Contains("d"));
            Assert.IsFalse(diff.Contains("e"));
            Assert.IsFalse(diff.Contains("b"));
            Assert.IsTrue(diff.Contains("a"));
            Assert.IsTrue(diff.Contains("c"));
        }