A Task’s exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was

by

If you create a Task, and you don’t ever call task.Wait() or try to retrieve the result of a Task<T>, when the task is collected by the garbage collector, it will tear down your application during finalization. For details, see MSDN’s page on Exception Handling in the TPL.

The best option here is to “handle” the exception. This can be done via a continuation – you can attach a continuation to the task, and log/swallow/etc the exception that occurs. This provides a clean way to log task exceptions, and can be written as a simple extension method, ie:

public static void LogExceptions(this Task task)
{
    task.ContinueWith( t =>
    {
         var aggException = t.Exception.Flatten();
         foreach(var exception in aggException.InnerExceptions)
             LogException(exception);
    }, 
    TaskContinuationOptions.OnlyOnFaulted);
}

With the above, you can prevent any task from tearing down the app, and logging it, via:

Task.Factory.StartNew( () => 
   { 
       // Do your work...
   }).LogExceptions();

Alternatively, you can subscribe to the TaskScheduler.UnobservedTaskException and handle it there.

More Related Contents:

  1. How to safely call an async method in C# without await
  2. Retry a task multiple times based on user input in case of an exception in task
  3. WPF global exception handler [duplicate]
  4. Globally catch exceptions in a WPF application?
  5. TAP global exception handler
  6. Execute task in background in WPF application
  7. When to use BlockingCollection and when ConcurrentBag instead of List?
  8. How to create a task (TPL) running a STA thread?
  9. Set ApartmentState on a Task
  10. Task continuation on UI thread
  11. Is Task.Factory.StartNew() guaranteed to use another thread than the calling thread?
  12. Difference between await and ContinueWith
  13. How to execute task in the wpf background while able to provide report and allow cancellation?
  14. What is the use for Task.FromResult in C#
  15. Waiting for async/await inside a task
  16. UnobservedTaskException being throw but it is handled by a TaskScheduler.UnobservedTaskException handler and a continuations OnlyOnFaulted handler [duplicate]
  17. How can I prevent synchronous continuations on a Task?
  18. How to avoid a System.Runtime.InteropServices.COMException?
  19. How can SynchronizationContext.Current of the main thread become null in a Windows Forms application?
  20. Can .NET Task instances go out of scope during run?
  21. How to handle Task.Run Exception
  22. Is it possible to get successful results from a Task.WhenAll when one of the tasks fails? [duplicate]
  23. Returning from a task without blocking UI thread
  24. Task.Run with Parameter(s)?
  25. Could not load file or assembly ‘System.Windows.Interactivity’ [duplicate]
  26. Task chaining (wait for the previous task to completed)
  27. Parallel execution for IO bound operations
  28. How to support ListBox SelectedItems binding with MVVM in a navigable application
  29. WPF binding not updating the view
  30. Output Console.WriteLine from WPF Windows Applications to actual console

Leave a Comment