Question

注意：取决于this quetion

您好。我有一个像这样的视图模型：

public class ViewModel {
    private readonly IPersonService _personService;
    private readonly ObservableCollection<SearchPersonModel> _foundedList;
    private readonly DispatcherTimer _timer;
    private readonly Dispatcher _dispatcher;
    private CancellationTokenSource _tokenSource;

    public SearchPatientViewModel(IPersonService personService) {
        _personService = personService;
        _foundedList = new ObservableCollection<SearchPersonModel>();
        _dispatcher = (/*CurrentApplication*/).Dispatcher;
        _timer = new DispatcherTimer(
            TimeSpan.FromMilliseconds(1000),
            DispatcherPriority.Normal,
            TimerCallBack,
            _dispatcher);
        _tokenSource = new CancellationTokenSource();
    }

    public string Term {
        get { return _term; }
        set {
            // implementing INotifyPropertyChanged
            if(_term== value)
                return;
            _term= value;
            OnPropertyChanged(() => Term);
            tokenSource.Cancel(); // canceling prev search query
            _timer.Stop(); // stop the timer to reset it
            // start it again to do a search query if user change not the term for 1000ms
            _timer.Start(); 
        }
    }

    private void TimerCallBack(object sender, EventArgs e) {
        _timer.Stop();
        _tokenSource = new CancellationTokenSource();
        var task = Task<IEnumerable<SearchPersonModel>>.Factory
            .StartNew(Search, _tokenSource.Token);
        _dispatcher.BeginInvoke((Action)(() => {
            _foundedList.Clear();
            foreach(var item in task.Result)
                _foundedList.Add(item);
        }), DispatcherPriority.Background);
    }

    private IEnumerable<SearchPersonModel> Search() {
        return _personService.DoSearch(this.Term);
    }

}

并在IPersonService实现中执行此操作：

public class PersonService : IPersonService {
    public IEnumerable<SearchPersonModel> DoSearch(string term){
        System.Threading.Thread.Sleep(10000);
        return some-search-result;
    }
}

但是，我希望在执行搜索查询时，GUI是免费的。但它冻结了！你知道我的错误在哪里吗？你能帮我吗？先谢谢！

Answer 1

问题是评估task.Result将阻止，直到查询完成。

最简单的选择可能是让Search方法在最后执行_dispatcher.BeginInvoke调用。

另一个选项 - 使用C＃5将变得更容易 - 将是为任务添加延续，以便在完成任务时可以更新UI。目前你使用Task.ContinueWith;使用C＃5，您可以使用async和await。

在Dispatcher.BeginInvoke或Task.StartNew时，GUI冻结

1 个答案: