Rx Workshop: Reactive Coincidence

Learn about the rich set of LINQ query operators available in Rx to query event streams.
I'm not sure I got this right as it seemed a little to easy...
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();
Got 404 page response when I click Download the Challenge link.