为什么异步Parallel.ForEach中的异常会使应用程序崩溃？

Question

如果在控制台应用程序中运行而不是将其抛出AggregateException并被外部捕获，以下的崩溃为什么会崩溃try/catch？

I've simplified the use case for the await for brevity, but in the relevant code I am indeed trying to execute an awaitable Task of importance.

var list = new List<string>() {"Error"};

        try
        {
            Parallel.ForEach(list, new ParallelOptions()
            {
                MaxDegreeOfParallelism = 8
            }, async listEntry =>
            {
                await Task.Delay(5000);
                throw new Exception("Exception");
            });
        }
        catch (Exception ex)
        {
            //never hits, the application crashes
        }

        Console.ReadLine();

I note that the following does not cause the application to fail, and an exception is indeed caught, but I do not understand what's really going on as to what is fundamentally different about the two contexts:

var list = new List<string>() {"Error"};

        try
        {
            Parallel.ForEach(list, new ParallelOptions()
            {
                MaxDegreeOfParallelism = 8
            }, listEntry =>
            {

                throw new Exception("Exception");
            });
        }
        catch (Exception ex)
        {
            //exception is caught, application continues
        }

        Console.ReadLine();

Answer 1

正如评论中已经提到的，您不应该混合使用async和Parallel.ForEach，它们不能一起使用。

您所观察到的是其中的后果之一：lambda作为async void方法被编译，并且当async void方法抛出时，异常将重新抛出，SynchronizationContext通常会导致应用程序崩溃。