ReactiveUI/Reactive Extensions：如何清除 ObservableAsPropertyHelper

Question

我正在使用 ReactiveUI 框架来搜索世界上的机场列表。

我已经设置了 ObservableAsPropertyHelper，它是 ViewModel 中 SearchTerm 属性的建议机场的输出。以下是 ObservableAsPropertyHelper 的定义。在视图中，我有一个绑定到此属性的列表框。我希望能够明确地清除列表框（因为一旦用户选择了建议的项目，我想用所选机场填充 SearchTerm 并清除建议的列表）。有没有一种优雅的方式来实现这一点？

var searchTerms = this.ObservableForProperty(x => x.SearchTerms).Where(x => canSearch).Value().Throttle(TimeSpan.FromMilliseconds(500));
var searchResults = searchTerms.SelectMany(SearchAirports);
var latestResults = searchTerms.CombineLatest(searchResults, (s, r) => r.SearchTerm != s ? null : r.AirportLiteWithWeights).Where(x => x != null);
_airportLiteWithWeights = latestResults.ToProperty(this, x => x.AirportLiteWithWeights);

Answer 1

我会这样做 - 这有点棘手，因为实际的事件序列会反馈到自身（即选择一个项目集 SearchTerms）

// The act of selecting an item is very ICommand'y, let's model it
// as such.
ReactiveCommand SuggestionItemSelected = new ReactiveCommand();

// Important to *not* signal a change here by touching the field
// so that we avoid a circular event chain
SuggestionItemSelected.Subscribe(x => _searchTerms = x);

// NB: Always provide a scheduler to Throttle!
var searchTerms = this.WhenAnyValue(x => x.SearchTerms)
    .Where(x => canSearch)
    .Throttle(TimeSpan.FromMilliseconds(500), RxApp.MainThreadScheduler);

// Select + Switch will do what you were trying to do with CombineLatest
var latestResults = searchTerms
    .Select(SearchAirports);
    .Switch()

// The listbox is the combination of *Either* the latest results, or the
// empty list if someone chooses an item
var latestResultsOrCleared = Observable.Merge(
    latestResults,
    SuggestionItemSelected.Select(_ => new List<Results>()));

latestResultsOrCleared
    .ToProperty(this, x => x.AirportLiteWithWeights, out _airportLiteWithWeights);