如何使用Reactive Extensions来限制SearchPane.SuggestionsRequested？

Question

Reactive Extensions允许我"观察"一系列事件.例如,当用户在Windows 8搜索窗格中键入其搜索查询时,会反复提出SuggestionsRequested(对于每个字母).如何利用Reactive Extensions来限制请求？

像这样的东西:

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

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));

安装Win for WinRT:http://nuget.org/packages/Rx-WinRT/ 了解更多信息: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));

您可能想要/需要使用不同的重载DistinctUntilChanged，例如使用不同的相等比较器或Func<TSource, TKey>重载：

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

那会做你想做的事。