从后台线程启动时，UI 线程上的任务继续

本文关键字：线程 任务 UI 继续 后台 启动 | 更新日期: 2023-09-27 18:34:26

如果以下代码在后台线程上运行，如何在主线程上"继续"？

  var task = Task.Factory.StartNew(() => Whatever());
  task.ContinueWith(NeedThisMethodToBeOnUiThread), TaskScheduler.FromCurrentSynchronizationContext())

上述操作将不起作用，因为当前同步上下文已经是后台线程。

从后台线程启动时，UI 线程上的任务继续

您需要从 UI 线程获取对 TaskScheduler.FromCurrentSynchronizationContext（） 的引用，并将其传递给延续。

与此类似。http://reedcopsey.com/2009/11/17/synchronizing-net-4-tasks-with-the-ui-thread/

private void Form1_Load(object sender, EventArgs e)
{
    // This requires a label titled "label1" on the form...
    // Get the UI thread's context
    var context = TaskScheduler.FromCurrentSynchronizationContext();
    this.label1.Text = "Starting task...";
    // Start a task - this runs on the background thread...
    Task task = Task.Factory.StartNew( () =>
        {
            // Do some fake work...
            double j = 100;
            Random rand = new Random();
            for (int i = 0; i < 10000000; ++i)
            {
                j *= rand.NextDouble();
            }
            // It's possible to start a task directly on
            // the UI thread, but not common...
            var token = Task.Factory.CancellationToken;
            Task.Factory.StartNew(() =>
            {
                this.label1.Text = "Task past first work section...";
            }, token, TaskCreationOptions.None, context);
            // Do a bit more work
            Thread.Sleep(1000);
        })
        // More commonly, we'll continue a task with a new task on
        // the UI thread, since this lets us update when our
        // "work" completes.
        .ContinueWith(_ => this.label1.Text = "Task Complete!", context);
}
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