关于任务结果的事件已完成

Question

可能的重复：
如何创建一个运行STA线程的任务（TPL）？

我正在使用以下代码：

var task = Task.Factory.StartNew<List<NewTwitterStatus>>(
        () => GetTweets(securityKeys),  
        TaskCreationOptions.LongRunning);
Dispatcher.BeginInvoke(DispatcherPriority.Background,
    new Action(() =>
    {
        var result = task.Result; // ERROR!!! The calling thread cannot access this object because a different thread owns it.
        RecentTweetList.ItemsSource = result;
        Visibility = result.Any() ? Visibility.Visible : Visibility.Hidden;
    }));

我遇到了错误：

var result = task.Result; // ERROR!!! The calling thread cannot access this object because a different thread owns it.

我需要做什么来解决此问题？

Answer 1

任务的想法是您可以链接它们：

  var task = Task.Factory.StartNew<List<NewTwitterStatus>>(
                            () => GetTweets(securityKeys),  
                            TaskCreationOptions.LongRunning
                        )
        .ContinueWith(tsk => EndTweets(tsk) );

    void EndTweets(Task<List<string>> tsk)
    {
        var strings = tsk.Result;
        // now you have your result, Dispatchar Invoke it to the Main thread
    }

Answer 2

您需要将调度程序调用转移到任务继续，看起来像这样：

var task = Task.Factory
    .StartNew<List<NewTwitterStatus>>(() => GetTweets(securityKeys), TaskCreationOptions.LongRunning)
    .ContinueWith<List<NewTwitterStatus>>(t =>
    {
        Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background,
            new Action(() =>
            {
                var result = t.Result;
                RecentTweetList.ItemsSource = result;
                Visibility = result.Any() ? Visibility.Visible : Visibility.Hidden;
            }));
    },
    CancellationToken.None,
    TaskContinuationOptions.None);

Answer 3

看起来您正在启动背景任务以开始阅读推文，然后启动另一个任务以读取结果而无需两者之间的任何协调。

我希望您的任务在继续进行中（请参阅http://msdn.microsoft.com/en-us/library/dd537609.aspx），在延续中，您可能需要调用UI线程....

var getTask = Task.Factory.StartNew(...);
var analyseTask = Task.Factory.StartNew<...>(
()=> 
Dispatcher.Invoke(RecentTweetList.ItemsSource = getTask.Result));