public void LookupMemberTest() { var v1 = (NSString)"1"; var v2 = (NSString)"2"; using (var st = new NSMutableSet <NSString> (v1)) { Assert.Throws <ArgumentNullException> (() => st.LookupMember((NSString)null), "LookupMember ANE 1"); Assert.AreSame(v1, st.LookupMember(v1), "LookupMember 1"); Assert.IsNull(st.LookupMember(v2), "LookupMember 2"); } }