OperationCanceledException VS GörevKanceledException Görev iptal edildiğinde

Question

Aşağıdaki kod, iptal edilmekte olan bir görev oluşturur. await İfadesi (durum 1), Wait() (durum 2) System.Threading.Tasks.TaskCanceledException (System.AggregateException içinde sarılmış) atarken System.OperationCanceledException'u atar.

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

public class Program 
{ 
    public static void Main() 
    { 
     Program.MainAsync().Wait(); 
    } 

    private static async Task MainAsync() 
    { 
     using(var cancellationTokenSource = new CancellationTokenSource()) 
     { 
      var token = cancellationTokenSource.Token; 
      const int cancelationCheckTimeout = 100; 

      var task = Task.Run(
       async() => 
       { 
        for (var i = 0; i < 100; i++) 
        { 
         token.ThrowIfCancellationRequested(); 
         Console.Write("."); 
         await Task.Delay(cancelationCheckTimeout); 
        } 
       }, 
       cancellationTokenSource.Token 
      ); 

      var cancelationDelay = 10 * cancelationCheckTimeout; 
      cancellationTokenSource.CancelAfter(cancelationDelay); 

      try 
      { 
       await task; // (1) 
       //task.Wait(); // (2) 
      } 
      catch(Exception ex) 
      { 
       Console.WriteLine(ex.ToString()); 
       Console.WriteLine($"Task.IsCanceled: {task.IsCanceled}"); 
       Console.WriteLine($"Task.IsFaulted: {task.IsFaulted}"); 
       Console.WriteLine($"Task.Exception: {((task.Exception == null) ? "null" : task.Exception.ToString())}"); 
      } 
     } 
    } 
} 

Durum 1 çıkışı:

..........System.OperationCanceledException: The operation was canceled. 
    at System.Threading.CancellationToken.ThrowIfCancellationRequested() 
    at Program.<>c__DisplayClass1_0.<<MainAsync>b__0>d.MoveNext() 
--- End of stack trace from previous location where exception was thrown --- 
    at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() 
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
    at Program.<MainAsync>d__1.MoveNext() 
Task.IsCanceled: True 
Task.IsFaulted: False 
Task.Exception: null 

Durum 2 çıkışı:

..........System.AggregateException: One or more errors occurred. ---> System.Threading.Tasks.TaskCanceledException: A task was canceled. 
    --- End of inner exception stack trace --- 
    at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken) 
    at System.Threading.Tasks.Task.Wait() 
    at Program.<MainAsync>d__1.MoveNext() 
---> (Inner Exception #0) System.Threading.Tasks.TaskCanceledException: A task was canceled.<--- 

Task.IsCanceled: True 
Task.IsFaulted: False 
Task.Exception: null 

Neden System.AggregateException 2 durumda bir iç durum olarak System.OperationCanceledException içermiyor?

Ben ThrowIfCancellationRequested()OperationCanceledException atar biliyoruz ve biz Task iptal (arızalı değil) durumuna alır her iki durumda da görebiliriz.

.NET API bir yöntem iptal her iki durumda da tutarlı davranış üretir, çünkü bu Kafamı kurcalayan - iptal edilen görev sadece TaskCanceledException atar:

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

public class Program 
{ 
    public static void Main() 
    { 
     Program.MainAsync().Wait(); 
    } 

    private static async Task MainAsync() 
    { 
     using(var cancellationTokenSource = new CancellationTokenSource()) 
     { 
      var token = cancellationTokenSource.Token; 

      var task = Task.Delay(1000, token); 
      cancellationTokenSource.CancelAfter(100); 

      try 
      { 
       await task; // (1) 
       //task.Wait(); // (2) 
      } 
      catch(Exception ex) 
      { 
       Console.WriteLine(ex.ToString()); 
       Console.WriteLine($"Task.IsCanceled: {task.IsCanceled}"); 
       Console.WriteLine($"Task.IsFaulted: {task.IsFaulted}"); 
       Console.WriteLine($"Task.Exception: {((task.Exception == null) ? "null" : task.Exception.ToString())}"); 
      } 
     } 
    } 
} 

Durum 1 çıkış:

System.Threading.Tasks.TaskCanceledException: A task was canceled. 
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
    at Program.<MainAsync>d__1.MoveNext() 
Task.IsCanceled: True 
Task.IsFaulted: False 
Task.Exception: null 

Durum 2 çıkışı:

System.AggregateException: One or more errors occurred. ---> System.Threading.Tasks.TaskCanceledException: A task was canceled. 
    --- End of inner exception stack trace --- 
    at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken) 
    at System.Threading.Tasks.Task.Wait() 
    at Program.<MainAsync>d__1.MoveNext() 
---> (Inner Exception #0) System.Threading.Tasks.TaskCanceledException: A task was canceled.<--- 

Task.IsCanceled: True 
Task.IsFaulted: False 
Task.Exception: null 

Answer 1

Buradaki fark,kullanılarak gelir.. Bu yöntem, iptal işlemini kontrol eder ve eğer istenirse OperationCanceledException'u TaskCanceledException (CancellationToken olarak anlaşılabilir) TPL'ye özel değildir. Sen reference source bakmak ve onu bu yöntemi çağırır görebilirsiniz:

private void ThrowOperationCanceledException() 
{ 
    throw new OperationCanceledException(Environment.GetResourceString("OperationCanceled"), this); 
} 

"Düzenli" iptal olsa gerçekten TaskCanceledException üretecektir.

cancellationTokenSource.Cancel(); 
var task = Task.Run(() => { }, cancellationTokenSource.Token); 
try 
{ 
    await task; 
} 
catch (Exception ex) 
{ 
    Console.WriteLine(ex.ToString()); 
    Console.WriteLine($"Task.IsCanceled: {task.IsCanceled}"); 
    Console.WriteLine($"Task.IsFaulted: {task.IsFaulted}"); 
    Console.WriteLine($"Task.Exception: {((task.Exception == null) ? "null" : task.Exception.ToString())}"); 
} 

Çıktı:

System.Threading.Tasks.TaskCanceledException: A task was canceled. 
    at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
    at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
    at System.Runtime.CompilerServices.TaskAwaiter.GetResult() 
    at Sandbox.Program.<MainAsync>d__1.MoveNext() 
Task.IsCanceled: True 
Task.IsFaulted: False 
Task.Exception: null 

Geleneksel Net yöntemler genellikle zaman uyumsuz API için CancellationToken.ThrowIfCancellationRequested kullanmayın Sen belirteci önce görev yayınlanmaya başlaması için bir şans vardı iptal ederek görebilirsiniz İşi başka bir iş parçacığına yüklerken uygundur. Bu yöntem, doğal olarak eşzamansız işlemler içindir, bu nedenle, iptal işlemi CancellationToken.Register (veya dahili InternalRegisterWithoutEC) kullanılarak izlenir.