C#和任务 - UI线程挂起 - 预异步/等待关键字

Question

当我无法访问我用来检索数据的客户端lib时,我试图理解异步获取一组数据的正确代码是什么.我指定了一个端点和一个日期范围,我应该检索一个播放列表列表.我现在所拥有的东西在Start()调用之后永远不会回来.注意:这是在WinForm中运行的.我试图更好地理解任务,而不只是想跳到等待或BackgroundWorker.我知道我在某个地方迷路了.

    private void GoButtonClick(object sender, EventArgs e)
    {
        string baseUrl = "http://someserver/api";
        var startDateTime = this._startDateTimePicker.Value;
        var endDateTime = this._endDateTimePicker.Value;
        _getPlaylistsFunc = delegate()
            {
                var client = new PlaylistExportClient(baseUrl);
                return client.GetPlaylistsByDateRange(startDateTime, endDateTime).ToList();
            };
        var task = new Task<List<Playlist>>(_getPlaylistsFunc);
        task.ContinueWith((t) => DisplayPlaylists(t.Result));
        task.Start();
    }

    private void DisplayPlaylists(List<Playlist> playlists)
    {
        _queueDataGridView.DataSource = playlists;
    }

更新 我做了这些更改,但现在应用程序似乎挂起了UI线程.

    private void GoButtonClick(object sender, EventArgs e)
    {
        string baseUrl = "http://someserver/api";
        var startDateTime = this._startDateTimePicker.Value;
        var endDateTime = this._endDateTimePicker.Value;
        var token = Task.Factory.CancellationToken;

        var context = TaskScheduler.FromCurrentSynchronizationContext();
        Task.Factory.StartNew(() =>
            {
                var client = new PlaylistExportClient(baseUrl);
                _queueDataGridView.DataSource = client.GetPlaylistsByDateRange(startDateTime, endDateTime).ToList();

            },token,TaskCreationOptions.None,context);

    }

Answer 1

看起来您正在后台线程中分配给 UI 控件的属性。这通常是坏消息。当您这样做时，WPF 通常会引发异常，但不确定 WinForms 是否如此。

在后台线程中捕获数据，但在将其分配给 UI 控件之前切换回主 UI 线程。尝试使用类似的方法将数据发布到 UI 线程

    var uiSync = SynchronizationContext.Current;
    Task.Factory.StartNew(() =>
        {
            var client = new PlaylistExportClient(baseUrl);
            var list = client.GetPlaylistsByDateRange(...).ToList();
            uiSync.Post(() => _queueDataGridView.DataSource = list, null);
        },token,TaskCreationOptions.None,context);