A Rx.NET hands-on-lab ex. 7 variant that uses TAP This version allows the user to type in a prefix string, for which the results will be looked up at the dictionary service. The results will be printed on the console.

TAP-to-IObservable.cs

static DictServiceSoapClient client = new DictServiceSoapClient("DictServiceSoapClient");

static TextBox txt = new TextBox();
static Form form = new Form() { Controls = { txt } };

static void Work()
{
  var input = Observable.FromEventPattern(txt, "TextChanged")
                .Throttle(TimeSpan.FromMilliseconds(200))
                .Select(x => ((TextBox)x.Sender).Text)
                .Where(x => x.Length > 2)
                .DistinctUntilChanged()
                .Do(x => Console.WriteLine("Input changed: {0}", x));

  var words = from term in input
              from response in RetrieveMatchesInDictForPrefix(term).TakeUntil(input)
              from word in WordsIn(response)
              select word;

  using (words.Subscribe(
    el => Console.WriteLine("Got word: {0}", el),
    ex => Console.WriteLine("Something went wrong: {0}", ex.Message),
    () => Console.WriteLine("Completed.")
  ))
  {
    Application.Run(form);
  }
}

static IObservable<DictionaryWord[]> RetrieveMatchesInDictForPrefix(string prefix)
{
  return Observable.FromAsync(() => RetrieveMatchInDictAsync(prefix));
}

static async Task<DictionaryWord[]> RetrieveMatchInDictAsync(string prefix)
{
  return await client.MatchInDictAsync("wn", prefix, "prefix");
}

static IObservable<string> WordsIn(DictionaryWord[] response)
{
  return response.ToObservable().Select(word => word.Word);
}