Catching Unhandled Exceptions in Child Threads in

Question

I have a WPF application that spins off several threads. I have defined a DispatcherUnhandledException event handler in App.xaml.cs that displays a detailed error message, and this handler gets called every time the UI thread encounters an exception. The problem is with the child threads: their unhandled exceptions never get handled. How do I do this?

Sample code:

private void Application_DispatcherUnhandledException(object sender, System.Windows.Threading.DispatcherUnhandledExceptionEventArgs e)
{
    MessageBox.Show("detailed error message");
}

private void Application_Startup(object sender, StartupEventArgs e)
{
    //...
    //If an Exception is thrown here, it is handled
    //...

    Thread[] threads = new Thread[numThreads];
    for(int i = 0; i < numThreads; i++)
    {
        threads[i] = new Thread(doWork);
        threads[i].Start();
    }
}

private void doWork()
{
    //...
    //Exception thrown here and is NOT handled
    //...
}

Edit: Once an unhandled exception occurs, I want to display an error message with a stack trace, and then exit the application.

Answer 1

This is by design, you should use a try/catch at the top-level of DoWork. Some threading models cater for this, take a look at the Backgroundworker for an example.

The .NET 4 Task class provides a nice interface to this problem. Until then, you will have to take care of it yourself, or use the BGW or IAsyncResult models.

Answer 2

Try hooking up to the AppDomain.CurrentDomain.UnhandledException event as well.