如何让BackgroundWorker ProgressChanged事件按顺序执行？

发布于 2024-12-14 01:04:37 字数 959 浏览 1 评论 0原文

考虑以下代码：

private static BackgroundWorker bg = new BackgroundWorker();

static void Main(string[] args) {
  bg.DoWork += bg_DoWork;
  bg.ProgressChanged += bg_ProgressChanged;
  bg.WorkerReportsProgress = true;
  bg.RunWorkerAsync();

  Thread.Sleep(10000);
}

static void bg_ProgressChanged(object sender, ProgressChangedEventArgs e) {
  Console.WriteLine(e.ProgressPercentage);
  Thread.Sleep(100);
  Console.WriteLine(e.ProgressPercentage);
}

static void bg_DoWork(object sender, DoWorkEventArgs e) {
  for (int i = 0; i < 10; i++) {
    bg.ReportProgress(i);
  }
}

运行时我得到以下输出：

0 1 1 2 0 3 2 3 5 4 4 6 5 7 7 8 6 9 8 9

据我所知，问题是BackgroundWorker 为每次调用ReportProgress 启动的线程之间的竞争条件。

我如何确保每个 bg_ProgressChanged 的整个主体按照我调用它们的顺序执行？这就是我想得到的

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9

结果为

原文

Consider the following code:

private static BackgroundWorker bg = new BackgroundWorker();

static void Main(string[] args) {
  bg.DoWork += bg_DoWork;
  bg.ProgressChanged += bg_ProgressChanged;
  bg.WorkerReportsProgress = true;
  bg.RunWorkerAsync();

  Thread.Sleep(10000);
}

static void bg_ProgressChanged(object sender, ProgressChangedEventArgs e) {
  Console.WriteLine(e.ProgressPercentage);
  Thread.Sleep(100);
  Console.WriteLine(e.ProgressPercentage);
}

static void bg_DoWork(object sender, DoWorkEventArgs e) {
  for (int i = 0; i < 10; i++) {
    bg.ReportProgress(i);
  }
}

When run I get the following output:

0
1
1
2
0
3
2
3
5
4
4
6
5
7
7
8
6
9
8
9

I understand that the issue is a race condition between the threads that BackgroundWorker starts for each call to ReportProgress.

How can I make sure that the whole body of each bg_ProgressChanged gets executed in the order I have called them?
That is I would like to get

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9

as a result.

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云裳 2024-12-21 01:04:37

BackgroundWorker 在调用 RunWorkerAsync() 的线程的当前 SynchronizationContext 上引发 ProgressChanged 事件。

默认 SynchronizationContext 在 ThreadPool 上运行回调，无需任何同步。

如果您在UI应用程序（WPF或WinForms）中使用BackgroundWorker，它将使用该UI平台的SynchronizationContext，它将按顺序执行回调。

回复收藏 0 原文

难如初 2024-12-21 01:04:37

不要使用这个解决方案！正如 SLAks 指出的那样，可能会导致僵局。

我似乎偶然发现了一个答案。我按以下方式更改了代码：

   [MethodImpl(MethodImplOptions.Synchronized)]
   static void bg_ProgressChanged(object sender, ProgressChangedEventArgs e) {
     Console.WriteLine(e.ProgressPercentage);
     Thread.Sleep(100);
     Console.WriteLine(e.ProgressPercentage);
   }

现在我得到了我想要的输出：

0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9

Do not use this solution!!! May lead to deadlocks as SLaks has pointed it out.

I seem to have stumbled upon an answer. I changed the code the following way:

   [MethodImpl(MethodImplOptions.Synchronized)]
   static void bg_ProgressChanged(object sender, ProgressChangedEventArgs e) {
     Console.WriteLine(e.ProgressPercentage);
     Thread.Sleep(100);
     Console.WriteLine(e.ProgressPercentage);
   }

and now I get the output I want: