如何处理 Task.Run 异常

问题描述

我在从 Task.Run 捕获异常时遇到问题，通过如下更改代码解决了该问题.我想知道这两种方式处理异常的区别:

I had a problem with catching the exception from Task.Run which was resolved by changing the code as follows. I'd like to know the difference between handling exceptions in these two ways :

在 Outside 方法中我无法捕获异常，但在 Inside 方法中我可以.

In the Outside method I can't catch the exception, but in the Inside method I can.

void Outside()
{
    try
    {
        Task.Run(() =>
        {
            int z = 0;
            int x = 1 / z;
        });
    }
    catch (Exception exception)
    {
        MessageBox.Show("Outside : " + exception.Message);
    }
}

void Inside()
{
    Task.Run(() =>
    {
        try
        {
            int z = 0;
            int x = 1 / z;
        }
        catch (Exception exception)
        {
            MessageBox.Show("Inside : "+exception.Message);
        }
    });
}

推荐答案

当任务运行时，它抛出的任何异常都会被保留，并在等待任务结果或任务完成时重新抛出.

When a task is run, any exceptions that it throws are retained and re-thrown when something waits for the task's result or for the task to complete.

>

Task.Run() 返回一个 Task 对象，您可以使用它来执行此操作，因此:

Task.Run() returns a Task object that you can use to do that, so:

var task = Task.Run(...)

try
{
    task.Wait(); // Rethrows any exception(s).
    ...

对于较新版本的 C#，您可以使用 await 而不是 Task.Wait():

For newer versions of C# you can use await instead ot Task.Wait():

try
{
    await Task.Run(...);
    ...

更整洁.

为了完整起见，这里有一个可编译的控制台应用程序，它演示了 await 的使用:

For completeness, here's a compilable console application that demonstrates the use of await:

using System;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main()
        {
            test().Wait();
        }

        static async Task test()
        {
            try
            {
                await Task.Run(() => throwsExceptionAfterOneSecond());
            }

            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }

        static void throwsExceptionAfterOneSecond()
        {
            Thread.Sleep(1000); // Sleep is for illustration only.
            throw new InvalidOperationException("Ooops");
        }
    }
}

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