如何从已取消的任务中获取内部异常
本文关键字:获取 内部 异常 任务 取消 | 更新日期: 2023-09-27 18:21:45
我有一个任务,在发生异常时,它会取消使用sme取消令牌的任务,并引发异常:
var cancellationTokenSource = new CancellationTokenSource();
var task1 = Task.Factory.StartNew(
() =>
{
try
{
// Do work
}
catch (Exception exception)
{
cancellationTokenSource.Cancel();
// rethrow the error
throw;
}
},
cancellationTokenSource.Token,
TaskCreationOptions.None,
taskScheduler);
我有另一个任务3(返回任务),它是任务1和任务2的延续,并使用相同的取消令牌:
return task3 =
Task.Factory.ContinueWhenAll(
new[] { task1, task2 },
tasks =>
{
// Do work
},
cancellationTokenSource.Token,
TaskContinuationOptions.None,
this.taskScheduler).Unwrap();
一旦任务1被取消,所有具有相同取消令牌的任务也将被取消。我需要得到task1抛出的内部异常,如何完成?
使用异步/等待和常规异常处理怎么样?不过它需要.NET 4.5。类似这样的东西(我不知道任务之间必须如何交互,所以你的代码可能会看起来完全不同):
using System;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
new MyClass().RunAsyncMethods();
Console.ReadLine();
}
public class MyClass
{
public async void RunAsyncMethods()
{
try
{
var cancellationTokenSource = new CancellationTokenSource();
var task1 = RunFirstTaskAsync(cancellationTokenSource);
var task2 = RunSecondTaskAsync(cancellationTokenSource);
await Task.WhenAll(task1, task2);
await RunThirdTaskAsync(cancellationTokenSource);
Console.WriteLine("Done");
}
catch (Exception exc)
{
Console.WriteLine(exc.Message);
}
}
public Task RunFirstTaskAsync(CancellationTokenSource cancelSource)
{
return Task.Run(() =>
{
try
{
Console.WriteLine("First Task is Running");
throw new Exception("Error happened in first task");
}
catch (Exception exception)
{
cancelSource.Cancel();
throw;
}
},
cancelSource.Token);
}
public Task RunSecondTaskAsync(CancellationTokenSource cancelSource)
{
return Task.Run(
() =>
{
Console.WriteLine("Second Task is Running");
},
cancelSource.Token);
}
public Task RunThirdTaskAsync(CancellationTokenSource cancelSource)
{
return Task.Run(
() =>
{
Console.WriteLine("Third Task is Running");
},
cancelSource.Token);
}
}
}
}
更新:我更新了代码以使用WhenAll。
UPDATE:更新代码以使用Task.Run方法创建任务,而不是使用冷任务。
UPDATE:您可以省略async/await(尽管我认为这样更好),并进行一些老式的TPL错误处理。简单地说,不要对task3(返回任务)使用取消令牌,只对它正在等待的任务使用取消令牌。当它们完成时(正常或通过异常/取消),您可以在task3中处理异常,如下所示:
// don't use the cancellation token for the third task as you used for the previous ones
var task3 = Task.Factory.ContinueWhenAll(
new[] { task1, task2 },
tasks =>
{
if (tasks[0].Exception != null)
{
tasks[0].Exception.Handle(exc =>
{
Console.WriteLine("First task failed :(");
return false; // signal that exception was handled, so it won't propagate
});
// add additional code here, or inside the Handle method above
}
if (tasks[1].Exception != null)
{
tasks[1].Exception.Handle(exc =>
{
Console.WriteLine("Second task failed :(");
return false; // signal that exception was handled, so it won't propagate
});
// add additional code here, or inside the Handle method above
}
// do the same for the rest of the tasks or iterate throught them with a foreach loop...
});