public void AsLookup() { var a = new System.Collections.Specialized.NameValueCollection { { "1", "one" }, { "1", "uno" }, }; var l = a.AsLookup(); Assert.AreEqual(1, l.Count); Assert.AreEqual(2, l["1"].Count()); Assert.AreEqual(0, l["2"].Count()); a.Add("2", "dos"); Assert.AreEqual(2, l.Count); Assert.AreEqual(1, l["2"].Count()); }