Observable.FromEvent<TextChangedEventArgs>(searchTextBox, "TextChanged")
          .Select(e => ((TextBox)e.Sender).Text)
          .Where(text => text.Length > 2)
          .Do(s => searchResults.Opacity = 0.5)                       
          .Throttle(TimeSpan.FromMilliseconds(400))
          .ObserveOnDispatcher()
          .Do(s => LoadingIndicator.Visibility = Visibility.Visible)   
          .SelectMany(txt => searchTwitter(txt))
          .Select(searchRes => ParseTwitterSearch(searchRes))
          .ObserveOnDispatcher()
          .Do(s => LoadingIndicator.Visibility = Visibility.Collapsed) 
          .Do(s => searchResults.Opacity = 1)                          
          .Subscribe(tweets => searchResults.ItemsSource = tweets);

// the uksnow twitter / bing mashup pipeline
Observable.Timer(TimeSpan.Zero, TimeSpan.FromSeconds(30))
          .SelectMany(ticks => searchTwitter("%23uksnow", _lastTweetId))
          .Select(searchResult => ParseTwitterSearch(searchResult))
          .ObserveOnDispatcher()
          .Do(tweet => AddTweets(tweet))                
          .Do(tweets => UpdateLastTweetId(tweets))
          .SelectMany(tweets => tweets)                                
          .SelectMany(tweet => ParseTweetToUKSnow(tweet))
          .SelectMany(snowTweet => searchBing(snowTweet))
          .ObserveOnDispatcher()                
          .Subscribe(geoTweet => AddSnow(geoTweet));
 
// every 5 minutes remove old snow from the map
Observable.Timer(TimeSpan.FromMinutes(5))
          .ObserveOnDispatcher()
          .Subscribe(i => RemoveOldSnowFromMap());