[英]How to get the inner exception from a cancelled task?
我有一個在發生異常的情況下取消使用sme取消令牌的任務並引發異常的任務:
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);
我還有另一個task3(返回任務),它是task1和task2的延續,並且使用相同的取消標記:
return task3 =
Task.Factory.ContinueWhenAll(
new[] { task1, task2 },
tasks =>
{
// Do work
},
cancellationTokenSource.Token,
TaskContinuationOptions.None,
this.taskScheduler).Unwrap();
一旦task1被取消,所有具有相同取消令牌的任務也將被取消。 我需要獲取task1引發的內部異常,該怎么辦?
如何使用異步/等待以及常規異常處理? 但是它將需要.NET 4.5。 這樣的事情(我不知道任務之間必須如何交互,因此您的代碼最終看起來可能會完全不同):
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:我更新了代碼以使用WhenAll。
更新:更新了代碼以使用Task.Run方法創建任務,而不是使用冷任務。
更新:您可以省略異步/等待(盡管我認為這樣更好),並進行一些老式的TPL錯誤處理。 根本不對任務3(返回任務)使用取消令牌,而僅對它正在等待的任務使用取消令牌。 當它們完成時(正常或通過異常/取消),您可以像下面這樣處理task3中的異常:
// 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...
});
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