Question

concurrent colleagues.

I need to be able to trap an exception that might be thrown from a background thread.

Let the code speak for itself (it is a bad code)

 public delegate bool CheckForUpdatesHandler(Uri uri);     public class UpdatesChecker {         public event AsyncCompletedEventHandler CheckForUpdatesAsyncCompleted;         protected virtual void OnCheckForUpdatesAsyncCompleted(AsyncCompletedEventArgs args) {             if (CheckForUpdatesAsyncCompleted != null)                 CheckForUpdatesAsyncCompleted(this, args);         }          public bool CheckForUpdates(Uri ftp) {                         Thread.Sleep(1000);             throw new Exception('bla');             return true;         }                public void CheckForUpdatesAsync(Uri ftp){                         var action = new CheckForUpdatesHandler(CheckForUpdates);             var c=action.BeginInvoke(ftp, delegate(IAsyncResult state) {                 OnCheckForUpdatesAsyncCompleted(new AsyncCompletedEventArgs(null, false, null));             }, null);         }         } 

Answer 1

With Delegate.BeginInvoke, the exception will be retrieved by calling .EndInvoke – which you must do anyway to prevent a leak.

With BackgroundWorker, it will appear on the completion event

On a vanilla Thread, an unhandled exception will tear down the process.

However, the simplest approach is: don’t let it throw…

    public bool CheckForUpdates(Uri ftp) {         try {             Thread.Sleep(1000);             throw new Exception('bla');             return true;         } catch (Exception ex) {             // raise an event, call a method/callback, do something         }     } 

If you currently aren’t using EndInvoke, then perhaps switch to the above pattern and just use ThreadPool directly (rather than Delegate.BeginInvoke).