For System.Timers.Timer, on separate thread, if SynchronizingObject is not set.
static System.Timers.Timer DummyTimer = null;
static void Main(string[] args)
{
try
{
Console.WriteLine("Main Thread Id: " + System.Threading.Thread.CurrentThread.ManagedThreadId);
DummyTimer = new System.Timers.Timer(1000 * 5); // 5 sec interval
DummyTimer.Enabled = true;
DummyTimer.Elapsed += new System.Timers.ElapsedEventHandler(OnDummyTimerFired);
DummyTimer.AutoReset = true;
DummyTimer.Start();
Console.WriteLine("Hit any key to exit");
Console.ReadLine();
}
catch (Exception Ex)
{
Console.WriteLine(Ex.Message);
}
return;
}
static void OnDummyTimerFired(object Sender, System.Timers.ElapsedEventArgs e)
{
Console.WriteLine(System.Threading.Thread.CurrentThread.ManagedThreadId);
return;
}
Output you'd see if DummyTimer fired on 5 seconds interval:
Main Thread Id: 9
12
12
12
12
12
...
So, as seen, OnDummyTimerFired is executed on Workers thread.
No, further complication - If you reduce interval to say 10 ms,
Main Thread Id: 9
11
13
12
22
17
...
This is because if prev execution of OnDummyTimerFired isn't done when next tick is fired, then .NET would create a new thread to do this job.
Complicating things further, "The System.Timers.Timer class provides an easy way to deal with this dilemma—it exposes a public SynchronizingObject property. Setting this property to an instance of a Windows Form (or a control on a Windows Form) will ensure that the code in your Elapsed event handler runs on the same thread on which the SynchronizingObject was instantiated."