在哪里可以找到 ThreadPool.SwitchTo 方法？

发布于 2024-10-14 16:34:46 字数 528 浏览 7 评论 0原文

我正在研究新的异步 CTP 并浏览一些示例代码，

我遇到了这段代码：

public async void button1_Click(object sender, EventArgs e) 
{ 
string text = txtInput.Text; 

await ThreadPool.SwitchTo(); // jump to the ThreadPool 

string result = ComputeOutput(text); 
string finalResult = ProcessOutput(result); 

await txtOutput.Dispatcher.SwitchTo(); // jump to the TextBox’s thread 

txtOutput.Text = finalResult; 
}

请问在哪里可以找到 ThreadPool.SwitchTo？ SwithcTo 方法不在 ThreadPool 类上

我有对 AsyncCtpLibrary.dll 的引用...但没有运气

原文

I am studying the new Async CTP and going through some sample code,

I came across this piece of code:

public async void button1_Click(object sender, EventArgs e) 
{ 
string text = txtInput.Text; 

await ThreadPool.SwitchTo(); // jump to the ThreadPool 

string result = ComputeOutput(text); 
string finalResult = ProcessOutput(result); 

await txtOutput.Dispatcher.SwitchTo(); // jump to the TextBox’s thread 

txtOutput.Text = finalResult; 
}

Please where do I find ThreadPool.SwitchTo? SwithcTo method is not on the ThreadPool class

i have a referece to AsyncCtpLibrary.dll ... but no luck

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折戟 2024-10-21 16:34:46

作为参考，CharlesO 在上面的评论中回答了他的问题：

好的，找到了，摘要：提供
与交互的方法
线程池。备注：ThreadPoolEx是一个
占位符。
公共共享函数 SwitchTo() As
System.Runtime.CompilerServices.YieldAwaitable
成员
System.Threading.ThreadPoolEx摘要：
创建一个等待
异步产生
等待时的线程池。

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￠好甜 2024-10-21 16:34:46

ThreadPool.SwitchTo 被删除可能是因为它是一个 anit 模式。考虑一下如果在切换回原始上下文之前抛出异常会发生什么。您不能使用finally 块作为防范该异常并切换回来的对策，因为await 不能出现在finally 块中。

public async void button1_Click(object sender, EventArgs e) 
{ 
  await ThreadPool.SwitchTo();
  try
  {
    // Do something dangerous here.
  }
  finally
  {
    await button1.Dispatcher.SwitchTo(); // COMPILE ERROR!
  }

}

当然，您可以开发自定义的可等待和等待者类型以准确实现已删除的内容。但是，使用 Task.Run¹ 比通过 await 中途切换上下文要好得多。

ThreadPool.SwitchTo was removed presumably because it is an anit-pattern. Consider what would happen if an exception were thrown before you switched back to the original context. You cannot use a finally block as a counter measure to guard against that exception and switch back because await cannot appear in finally blocks.

public async void button1_Click(object sender, EventArgs e) 
{ 
  await ThreadPool.SwitchTo();
  try
  {
    // Do something dangerous here.
  }
  finally
  {
    await button1.Dispatcher.SwitchTo(); // COMPILE ERROR!
  }

}

You can, of course, develop custom awaitable and awaiter types to achieve exactly what was removed. However, it is far better to use Task.Run¹ than to switch contexts midstream via await.

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