何时使用TaskEx.Run与TaskEx.RunEx

问题描述

我想了解什么时候使用 TaskEx.Run 。我已经提供了两个code样我写了下面这产生相同的结果。我看不出就是为什么我会采取 TaskEx.RunEx 的办法，我敢肯定有一个很好的理由，是希望有人可以填补我

 异步任务的DoWork（的CancellationToken cancelToken，IProgress＆LT;串GT;进度）
{
    INT I = 0;
    TaskEx.RunEx（异步（）=＆GT;
        {
            而（！cancelToken.IsCancellationRequested）
            {
                progress.Report（我的ToString ++（））;
                等待TaskEx.Delay（1 cancelToken）;
            }
        }，cancelToken）;
}
私人无效Button_Click（对象发件人，RoutedEventArgs E）
{
    如果（button.Content.ToString（）==开始）
    {
        button.Content =停止;
        cts.Dispose（）;
        CTS =新CancellationTokenSource（）;
        listBox.Items.Clear（）;
        IProgress＆LT;串GT;进度=新进展＆LT;串将（S = GT;
        {
            listBox.Items.Add（多个）;
            listBox.ScrollIntoView（listBox.Items [listBox.Items.Count  -  1]）;
        }）;
        DoWork的（cts.Token，进度）;
    }
    其他
    {
        button.Content =开始;
        cts.Cancel（）;
    }
}
 

我能做到像这样相同的结果。

 异步任务的DoWork（的CancellationToken cancelToken）
    {
        INT I = 0;
        而（！cancelToken.IsCancellationRequested）
        {
            listBox.Items.Add（我++）;
            listBox.ScrollIntoView（listBox.Items [listBox.Items.Count  -  1]）;
            等待TaskEx.Delay（100，cancelToken）;        }
    }    私人无效Button_Click（对象发件人，RoutedEventArgs E）
    {
        如果（button.Content.ToString（）==开始）
        {
            button.Content =停止;
            cts.Dispose（）;
            CTS =新CancellationTokenSource（）;
            listBox.Items.Clear（）;
            DoWork的（cts.Token）;
        }
        其他
        {
            button.Content =开始;
            cts.Cancel（）;
        }
    }
 

解决方案

使用 TaskEx.Run 当你想运行一个线程池环境同步code。

使用 TaskEx.RunEx 当你想在一个线程池环境中运行的异步code。

斯蒂芬Toub在行为相关的差异2的博客文章：

这只是你有的几个选项之一。如果你没有使用运行 / RunEx ，那么你不应该。使用简单的异步方法，并且只使用运行 / RunEx 如果你需要在后台运行的东西。

I'm trying to understand when to use TaskEx.Run. I have provided two code sample i wrote below that produce the same result. What i fail to see is why i would take the TaskEx.RunEx approach, I'm sure there is a good reason and was hoping someone could fill me in.

async Task DoWork(CancellationToken cancelToken, IProgress<string> progress)
{
    int i = 0;
    TaskEx.RunEx(async () =>
        {
            while (!cancelToken.IsCancellationRequested)
            {
                progress.Report(i++.ToString());
                await TaskEx.Delay(1, cancelToken);
            }
        }, cancelToken);
}
private void Button_Click(object sender, RoutedEventArgs e)
{
    if (button.Content.ToString() == "Start")
    {
        button.Content = "Stop";
        cts.Dispose();
        cts = new CancellationTokenSource();
        listBox.Items.Clear();
        IProgress<string> progress = new Progress<string>(s =>
        {
            listBox.Items.Add(s);
            listBox.ScrollIntoView(listBox.Items[listBox.Items.Count - 1]);
        });
        DoWork(cts.Token, progress);
    }
    else
    {
        button.Content = "Start";
        cts.Cancel();
    }
}

I can achieve the same results like so

  async Task DoWork(CancellationToken cancelToken)
    {
        int i = 0;
        while (!cancelToken.IsCancellationRequested)
        {
            listBox.Items.Add(i++);
            listBox.ScrollIntoView(listBox.Items[listBox.Items.Count - 1]);
            await TaskEx.Delay(100, cancelToken);

        }
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        if (button.Content.ToString() == "Start")
        {
            button.Content = "Stop";
            cts.Dispose();
            cts = new CancellationTokenSource();
            listBox.Items.Clear();
            DoWork(cts.Token);
        }
        else
        {
            button.Content = "Start";
            cts.Cancel();
        }
    }

解决方案

Use TaskEx.Run when you want to run synchronous code in a thread pool context.

Use TaskEx.RunEx when you want to run asynchronous code in a thread pool context.

Stephen Toub has two blog posts related to the difference in behavior:

• Potential pitfalls to avoid when passing around async lambdas
• Task.Run vs Task.Factory.StartNew

This is only one of several options you have for creating tasks. If you do not have to use Run/RunEx, then you should not. Use simple async methods, and only use Run/RunEx if you need to run something in the background.

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