Question

I’m using a Threading.Timer to execute a task on the hour every hour, but when the timer ticks, the app always crashes when processing the code to execute in the tick. It crashes with no exceptions or warnings, even if I put the whole thin in a try/catch. Very strange. Below is my setup and any help would be appreciated! It seems like crashes when it tries to access the TextBox GrepCmdTextBox, but I thought reading from another thread was okay, just not writing.

Setting up timer:

var timeOfDay = DateTime.Now.TimeOfDay;
var nextHour = TimeSpan.FromHours(Math.Ceiling(timeOfDay.TotalHours));
var delta = (nextHour - timeOfDay).TotalMilliseconds;
System.Threading.Timer NextHourTimer = new System.Threading.Timer(new System.Threading.TimerCallback(NextHourTimer_Tick), null, (long)delta, (long)TimeSpan.FromHours(1).TotalMilliseconds);

Tick event:

private void NextHourTimer_Tick(object sender)
    {
        // If thread is not null and is busy, cancel and restart
        if (MonitoringThread != null)
        {
            if (MonitoringThread.TailThread.IsBusy)
            {
                MonitoringThread.TailThread.CancelAsync();
                System.Threading.Thread.Sleep(50);

                // Get grep command, if specified
                string optionalGrep = String.Empty;
                if (GrepCmdTextBox.Text.StartsWith("grep") || GrepCmdTextBox.Text.StartsWith("egrep"))
                    optionalGrep = " | " + GrepCmdTextBox.Text;

                MonitoringThread.TailThread.RunWorkerAsync(optionalGrep);
            }
        }
    }

Answer 1

Cancelling the asynchronous process can take time, the background thread will have to ‘finalize’, returning from DoWork() and waiting for an opportunity to run the RunWorkerCompleted event, if any.

Instead of cancellation, in this case it would be better to cancel then Dispose() the object, creating a new BGW, as they are as ‘cheap-as-chips’.

I hope this helps.