如何使用Reactive Extensions來限制SearchPane.SuggestionsRequested？

Question

反應性擴展允許我「觀察」一系列事件。例如，當用戶在Windows 8搜索窗格中鍵入搜索查詢時，SuggestionRequested會一遍又一遍（每個字母）引發。我如何利用Reactive Extensions來抑制請求？

事情是這樣的：

SearchPane.GetForCurrentView().SuggestionsRequested += (s, e) => 
{ 
    if (e.QueryText.Length < 3) 
     return; 
    // TODO: if identical to the last request, return; 
    // TODO: if asked less than 500ms ago, return; 
}; 

解決方案

System.Reactive.Linq.Observable.FromEventPattern<Windows.ApplicationModel.Search.SearchPaneSuggestionsRequestedEventArgs> 
    (Windows.ApplicationModel.Search.SearchPane.GetForCurrentView(), "SuggestionsRequested") 
    .Throttle(TimeSpan.FromMilliseconds(500), System.Reactive.Concurrency.Scheduler.CurrentThread) 
    .Where(x => x.EventArgs.QueryText.Length > 3) 
    .DistinctUntilChanged(x => x.EventArgs.QueryText.Trim()) 
    .Subscribe(x => HandleSuggestions(x.EventArgs)); 

對WinRT的安裝RX：http://nuget.org/packages/Rx-WinRT/ 瞭解更多：http://blogs.msdn.com/b/rxteam/archive/2012/08/15/reactive-extensions-v2-0-has-arrived.aspx

Answer 1

有Throttle和DistinctUntilChanged方法。

System.Reactive.Linq.Observable.FromEventPattern<Windows.ApplicationModel.Search.SearchPaneSuggestionsRequestedEventArgs> 
    (Windows.ApplicationModel.Search.SearchPane.GetForCurrentView(), "SuggestionsRequested") 
    .Throttle(TimeSpan.FromMilliseconds(500), System.Reactive.Concurrency.Scheduler.CurrentThread) 
    .Where(x => x.EventArgs.QueryText.Length > 3) 
    .DistinctUntilChanged(x => x.EventArgs.QueryText.Trim()) 
    .Subscribe(x => HandleSuggestions(x.EventArgs)); 

你可能想/需要使用不同的過載DistinctUntilChanged，例如使用不同的相等比較器或Func<TSource, TKey>過載：

.DistinctUntilChanged(e => e.QueryText.Trim()) 

會做你想要什麼。