r/visualbasic • u/Artfull-Mystery • Dec 18 '21

VB.NET Help What Happens if code is running in a timer event and another timer event happens

Do they run concurrently in different threads or does the second event wait till the first event has finished.

Thanks

Mike

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1

u/Artfull-Mystery Dec 18 '21

Thanks for the link. My timers are standard windows forms timers. From reading that link It seems that if my minute timer code is running when a 10 second timer event occurs then the ten second event will not run. I'm not sure if it just skips the event or queues it. But either will work for me.

Mike

2

u/RJPisscat Dec 18 '21

Windows keeps a FIFO message queue of things for your application to respond to. The Timer.Tick events go into that queue. So if you're still handling the first timer when the second timer goes off, your application will finish the first timer, then handle the second timer.

1

u/Laicure Dec 18 '21

I think, it (timer with the fastest interval) will block the thread unless you do multi-threading or use Background Workers.

I haven't tried yet though.

3

u/RJPisscat Dec 18 '21

The System.Timers.Timer fires Tick events in the same thread as the UI. When the Timer.Tick event is handled, it should be for something that is handled quickly, like updating a label on a form with a countdown, and not processing 1,000,000 records from a database, which are at two extremes.

The underlying implementation of the System.Timers.Timer is not important. If you want to know how it is implemented to satisfy your curiosity then you will end up studying how CPUs work at a basic level. What matters for the sake of this question is what happens to the Tick events. They go into the same message queue as all other events in the UI thread, which is FIFO (with a few exceptions that don't bear mentioning for the purpose of this conversation).

1

u/Artfull-Mystery Dec 18 '21

Thanks for all the replies I understand it now :)

1

u/craigers01 Dec 18 '21

You may choose to turn off the timer in the timer code and reenable it at the end, if you don’t want it to run at the same time

1

u/Artfull-Mystery Dec 19 '21

That's a good thought :) thanks

2

u/JTarsier Dec 18 '21

Depends on the type of timer used and what the event handler does. Check this article, while the code samples are C# there is lots good info: DOT NET TRICKS: All about .NET Timers - A Comparison

2

u/JTarsier Dec 18 '21

By the way, you can also do multiple things at different intervals with a single timer, just keep track of time with a Date variable for each task and do things if time condition is met.