如何处理Task.Run异常 [英] How to handle Task.Run Exception

问题描述

我在从Task捕获异常时遇到问题.运行我更改了代码，问题解决了.我愿意找出以两种方式运行Task.Run中的异常之间的区别:

在Outside函数中，我无法捕获异常，但在Inside函数中，我可以捕获异常.

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);
        }
    });
}

解决方案

运行任务时，它所引发的任何异常都将保留，并在某些等待任务结果或任务完成的情况下重新抛出. >

Task.Run()返回一个可用于执行此操作的Task对象，因此:

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():

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

整整齐齐.

---

为完整起见，这是一个可编译的控制台应用程序，演示了await的用法:

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");
        }
    }
}

I had a problem with catching my exception from Task.Run I changed my code and my problem solved. I'm willing to figure out what is the difference between handling exceptions inside Task.Run in these two ways :

In Outside function I can't catch the exception but in Inside I can catch it.

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);
        }
    });
}

解决方案

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

var task = Task.Run(...)

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

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

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

which is much neater.

---

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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