BackgroundWorker and exceptions

Got a bit confused at work today when a piece of software seemingly halted in a place where it should not have been possible.

After looking at the code for a while I found something like the following:

            BackgroundWorker bgw = new BackgroundWorker();
           bgw.DoWork += new DoWorkEventHandler(bgw_DoWork);
           bgw.RunWorkerAsync();           

where bgw_DoWork was (basically) implemented thusly:

        void bgw_DoWork(object sender, DoWorkEventArgs e)
       {
           // ...
            throw new Exception("things went bad");
       }

If you try it out (outside the debugger) you'll notice that the exception is silently swallowed !?!

The moral of the story:

If you use Background worker, either implement a catch all handler within the DoWork method or, hook the RunWorkerCompleted event and check RunWorkerCompletedEventArgs.Error for non-null value.