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TaskScheduler.UnobservedTaskException is still being raised even when the exception is trapped. This is working in the stable channel, and had been working in the alpha channel until recently, so I'm guessing it's a recent change.
This is reproducible in Xamarin.iOS 7.0.6, and works correctly in 7.0.4.
Here's a simple repro:
public partial class UnhandledExceptionReproViewController : UIViewController
public override async void ViewDidLoad()
TaskScheduler.UnobservedTaskException += (sender, e) =>
if (e.Exception != null)
new UIAlertView("unobserved task exception", e.Exception.Message, null, "Ok", null).Show());
catch (Exception ex)
new UIAlertView("trapped exception", ex.Message, null, "Ok", null).Show();
private async Task getResult()
throw new Exception("boom");
I have verified this issue and getting TaskScheduler.UnobservedTaskException exception with current build, following are the verified steps:
1. Created a sample iOS (iPhone single view application)
2. Add above code into view controller cs file.
3. Debug application.
Refer screen shot: http://screencast.com/t/asl6xhf12
XS 4.2.3 (build 23)
X iOs 18.104.22.168
Also I have verified on stable build, working fine.
XS 4.2.2 (build 2)
X iOs 22.214.171.124
Fixed in mono master
Fix pushed to the monotouch 7.0.6 branch:
Using Xamarin.iOS 126.96.36.199, the exception is properly trapped. See: http://screencast.com/t/uufCsj9v
There's no mention of this fix in the new 7.0.6 maintenance release. Is it included?
Yes, this is included in the 7.0.6 release.