ASP.NET C# thread aborted exception?

Question

i am trying to build a small email worker that sends my emails. The email worker operates in its own thread. The global.asax starts the thread and then it runs for one round before throwing this exception. I have been trying to find out where it throws it, but it seems to be different each time. The records are printed to the text file so that works, maybe the dispose functions?

This is the exception thrown:

Starting a new round in the email worker for-loop
Going to sleep in the email worker for-loop
A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll
An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code

This is the code for the EmailWorker

public static class EmailWorker
{
    public static void Work()
    {
        TimeSpan sleepTime = new TimeSpan(0, 1, 0);

        for (; ; )
        {
            Debug.WriteLine("Starting a new round in the email worker for-loop");
            try
            {
                // Get the records
                CS_Code.UtopiaDataContext db = new CS_Code.UtopiaDataContext(); 
                List<CS_Code.Global_Email> emailsToSend = (from xx in db.Global_Emails select xx).ToList();


                // Write the records to a file (for now)
                TextWriter writer = new StreamWriter(@"test.txt", true); // For debugging
                foreach (var email in emailsToSend)
                    writer.WriteLine("To: " + email.Email_Address + ", Subject: " + email.Subject + ", uid:" + email.UserName.ToString());
                writer.Close();
                writer.Dispose();

                // Delete the used records from the database
                foreach (var email in emailsToSend)
                    db.Global_Emails.DeleteOnSubmit(email);
                db.SubmitChanges();
                db.Dispose();


                Debug.WriteLine("Going to sleep in the email worker for-loop");
                Thread.Sleep(sleepTime); // Sleep for 1 minute.
                Debug.WriteLine("Just woke up in the email worker for-loop");
            }
            catch (Exception e)
            {               
                Debug.WriteLine(e.Message);
                break;
            }
        }
    }
}

This is the global.asax file that starts everything:

private static Thread EmailWorkerThread { get; set; }

void Application_Start(object sender, EventArgs e)
{
    // Email worker thread
    if ((EmailWorkerThread == null) || (!EmailWorkerThread.IsAlive))
    {
        ThreadStart ts = new ThreadStart(EmailWorker.Work);
        EmailWorkerThread = new Thread(ts);
        EmailWorkerThread.Start();
    }
}

void Application_End(object sender, EventArgs e)
{
    // Email worker thread
    if ((EmailWorkerThread != null) || (EmailWorkerThread.IsAlive))
        EmailWorkerThread.Abort();
    EmailWorkerThread = null;
}

Answer 1

The thread that you are creating is being aborted by asp.net. Creating long running threads are a major no-no in asp.net.

A we have a working workaround, that we are not proud of... Create a timer that process pending emails.

static Timer processTimer; // declare static at service level

// At the static constructor:
processTimer = new Timer(new TimerCallback(TimerTick), 60000, 10000, defaultInterval); //wait a minute before begin (dueTime = 60000)

To be extra carefull, at the Timer_Tick event, handle at most N emails, so the timer tick ends, and a new one rises...

This is working on our production environment...