使用异步方法等待Task.Run不会在正确的线程上引发异常 [英] Awaiting Task.Run with async method does not throw exception on correct thread

问题描述

当运行下面的测试方法时，我发现即使我等待引发异常的任务，测试仍会通过.此外，将弹出一个单独的窗口，提示"QTAgent.exe已停止工作".这表明异常不会传播到运行测试的线程，而是杀死了一个单独的线程.

When running the test method below, I found that even though I await a task that throws an exception, the test passes. Furthermore, a separate window pops up saying "QTAgent.exe has stopped working". This indicates that the exception is not propagated to the thread running the test and instead kills a separate thread.

我想知道为什么会这样.另外，由于这似乎无法正常工作，我应该如何在线程池线程上运行异步方法?

I would like to know why this happens. Also, since this doesn't appear to work as intended, how should I run an async method on a thread pool thread?

请注意，如果我更改了它，以便如果func不是异步的，则异常会按预期在测试线程中引发.

Note that if I change it so that if func is not async, the exception is thrown in the test thread as expected.

 [TestMethod]
 public async Task TestWeirdTaskBehavior()
 {
      Action func = async () =>
      {
           await Task.Delay(0);
           throw new InvalidOperationException();
      };
      await Task.Run(func);
 }

推荐答案

简单的调整:

[TestMethod]
public async Task TestWeirdTaskBehavior()
{
    Func<Task> func = async () =>
    {
        await Task.Delay(0);
        throw new InvalidOperationException();
    };
    await Task.Run(func);
}

您的 Action 本质上是一个 async void .如果要等待它或将其包装在另一个 Task 中，则需要编译器为您吐出 Task .在您的原始代码段中，外部任务( Task.Run(...))一旦内部任务达到第一个 await ，即 ，就会完成>引发异常.

Your Action is essentially an async void. You need the compiler to spit out a Task for you if you want to await it or wrap it in another Task. In your original snippet the outer task (Task.Run(...)) completes as soon as the inner task hits the first await, before the exception is thrown.

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