Systems.timer.timer unwanted multithreading

Question

I recently switched my code from using the windows.forms.timer to the systems.timer.timer and it has resulted in a multithreading error. I'm using the timer to trigger just one event so multithreading shouldn't be an issue. To give more detail I have implemented the timer at follows: At the top of the class I have:

Private Shared timr1sec As System.Timers.Timer

When the program loads (Private Sub Test_load):

timr1sec = New System.Timers.Timer(1000)
AddHandler timr1sec.Elapsed, AddressOf OnTimedEvent

In OnTimedEvent I call several subroutines, and write some data to the screen using a ListView object. VisualExpress throws the multithreading error on the last line of this code, which is in OnTimedEvent

    Dim itm As New ListViewItem(str(0))

    itm.SubItems.Add(str(1))
    itm.SubItems.Add(str(2))
    itm.SubItems.Add(str(3))
    itm.SubItems.Add(str(4))
    itm.SubItems.Add(str(5))

    ListView1.Items.AddRange(New ListViewItem() {itm})

Any idea what it is about this new timer that's causing VisualExpress to say I'm multithreading?

see also: stackoverflow.com/questions/191903/which-net-timer-to-use — Rob Allen
– Rob Allen, Commented Jul 14, 2011 at 18:39

SLaks · Accepted Answer · 2011-07-14 18:36:29Z

3

System.Timers.Timer raises its Elapsed event on a threadpool thread.

You should use a System.Windows.Forms.Timer, which always uses the UI thread.

If you really want to, you could set the SynchronizingObject property on the Timers.Timer to tell it to marshal its events to the UI thread, but there's no point.

answered Jul 14, 2011 at 18:36

SLaks

891k182 gold badges1.9k silver badges2k bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

vortex Over a year ago

I was using System.Windows.Forms.Timer but I'm using the timer as a stopwatch and as I've found out Windows.Forms.Timer is not designed for this. A nice explanation is here; msdn.microsoft.com/en-us/magazine/cc164015.aspx

vortex Over a year ago

I've found a few examples of synchronizingObject but I'm not sure how this applies. Could you tell me more or point me to a good example?

SLaks Over a year ago

Timers.Timer can call SynchronizingObject.BeginInvoke to run the callback in the UI thread

vortex Over a year ago

OK, I've set timr1sec.SynchronizingObject = textbox1 and that synchronized the timer thread with the form. Thanks for your help!

SLaks Over a year ago

Note that by setting SynchronizingObject, you will lose precision, since you need to wait for the message loop before your handler runs.

Collectives™ on Stack Overflow

Systems.timer.timer unwanted multithreading

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related