var lookup = textChanged
                            .Select(_ => txt.Text)
                            .DistinctUntilChanged()
                            .Throttle(TimeSpan.FromMilliseconds(200))
                            .Do(text => Console.WriteLine("TextChanged: {0}", text))
                            .Where(text => text.Length >= 3)
                            .Do(text => Console.WriteLine("Lookup: {0}", text));

var results = lookup
                          .Select(text => getSuggestions(text))
                          .Switch();

posted by N2Cheval

posted by thanhym