Task.Run和UI最新进展 [英] Task.Run and UI Progress Updates

问题描述

此代码来自斯蒂芬·克利里的博客，并给出了如何使用Task.Run时，报告进度的例子。我想知道为什么会出现与更新UI，我指的是为什么没有则启动不需要跨线程问题？

 专用异步无效button2_Click（对象发件人，EventArgs五）
 {
变种progressHandler =新进展<字符串>（价值=> 
 {
 label2.Text =价值; 
}）; 
 VAR进度= progressHandler作为IProgress<字符串取代; 
等待Task.Run（（）=> 
 {
的for（int i = 0;！我= 100; ++ I）
 {
如果（ ！进展=空）
 progress.Report（阶段+ I）; 
 Thread.sleep代码（100）; 
} 
}）; 
 label2.Text =已完成。 
} 
  

解决方案

进展< T> 捕捉当前 SynchronisationContext 当它被实例化。每当你叫报告，偷偷代表们将捕获的上下文。在该示例中，所捕获的上下文是用户界面中，这意味着没有发生异常。

This code snippet is from Stephen Cleary's blog and gives an example of how to report progress when using Task.Run. I would like to know why there are no cross thread issues with updating the UI, by which I mean why is invoke not required?

private async void button2_Click(object sender, EventArgs e)
{
    var progressHandler = new Progress<string>(value =>
    {
        label2.Text = value;
    });
    var progress = progressHandler as IProgress<string>;
    await Task.Run(() =>
    {
        for (int i = 0; i != 100; ++i)
        {
            if (progress != null)
                progress.Report("Stage " + i);
            Thread.Sleep(100);
        }
    });
    label2.Text = "Completed.";
}

解决方案

Progress<T> catches the current SynchronisationContext when it is instantiated. Whenever you call Report, it secretly delegates that to the captured context. In the example, the captured context is the UI, meaning that no exceptions occur.

这篇关于Task.Run和UI最新进展的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！