c# – 在哪里处理Task抛出的异常

我在单独的任务中执行一些轮询IO循环.这些循环可能会遇到异常.如果遇到异常,我想提醒调用者,以便它可以：

>记录下来
>杀死所有IO线程
>重置连接
>重启IO线程

用户界面必须保持响应.处理此方案的首选方法是什么？我在下面列出了一个说明性的程序.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TaskExceptionCatching
{
    class Program
    {
        static void Main(string[] args)
        {
            startLoops();

            System.Console.WriteLine("Type 'Exit' when you're ready to stop.");
            while (System.Console.ReadLine() != "Exit")
            {
                System.Console.WriteLine("SerIoUsly,just type 'Exit' when you're ready to stop.");
            }
        }

        static private void startLoops()
        {
            System.Console.WriteLine("Starting fizzLoop.");
            var fizzTask = Task.Factory.StartNew(new Action(fizzLoop));

            System.Console.WriteLine("Starting buzzLoop.");
            var buzzTask = Task.Factory.StartNew(new Action(buzzLoop));
        }

        static private void fizzLoop()
        {
            while (true)
            {
                //simulate something error prone,like some risky IO
                System.Threading.Thread.Sleep(200);
                bool isErr = (new Random().Next(1,100) == 10);
                if (isErr)
                    throw new Exception("Fizz got an exception.");
            }
        }

        static private void buzzLoop()
        {
            while (true)
            {
                //simulate something error prone,100) == 10);
                if (isErr)
                    throw new Exception("Buzz got an exception.");
            }
        }
    }
}

解决方法

这可能是异常void方法可能很方便的极少数情况之一：

static async void StartAndMonitorAsync(Func<Task> taskFunc)
{
    while (true)
    {
        var task = taskFunc();
        try
        {
            await task;
            // process the result if needed
            return;
        }
        catch (Exception ex)
        {
            // log the error
            System.Console.WriteLine("Error: {0},restarting...",ex.Message);
        }
        // do other stuff before restarting (if any)
    }
}

static private void startLoops()
{
    System.Console.WriteLine("Starting fizzLoop.");
    StartAndMonitorAsync(() => Task.Factory.StartNew(new Action(fizzLoop)));

    System.Console.WriteLine("Starting buzzLoop.");
    StartAndMonitorAsync(() => Task.Factory.StartNew(new Action(buzzLoop)));
}

如果你不能使用async / await,可以使用Task.ContinueWith实现类似的逻辑.

如果可以多次调用startLoops(当任务已经“在飞行中”时),则需要使用CancelltionToken(“A pattern for self-cancelling and restarting task”中的更多详细信息)向StartAndMonitorAsync及其启动的任务添加取消逻辑.