Re: Executing a method in a given thread context

Jeffrey,

Thanks for your very interesting answer. I will have a look at the "timer
trick".
This raise some more questions:
1) What is the impact of relying on a winform control when my non-visual
component is used in a non GUI application such as a console application, a
service application, a web application, or whatever ?
2) What is the impact of using P/Invoke ? I there anything to avoid ? Should
I use some attributes to mark the assemblies or the classes as safe and
secure ?
3) Is the "UI thread" the main thread of an application or - as said by
someone in a previous answer to my question - any thread which has a message
pump ? As I understand, it is the user interface thread aka the main thread.
4) If answer to 3 is "main thread", then how do I apply the "timer trick" to
a worker thread ?

--
Francois PIETTE
http://www.overbyte.be


""Jeffrey Tan[MSFT]"" <jetan@xxxxxxxxxxxxxxxxxxxx> a écrit dans le message
de news:iScdys3uGHA.492@xxxxxxxxxxxxxxxxxxxxxxxx
Hi Francois,

Before I read this thread, you have several discussion with the community
members alrealdy. To not miss the key point, I want to recap my understand
of this issue.

Based on my understanding, you want to know some best practise of
cross-thread operation in .Net winform and you do not like the pure Win32
p/invoke approach.

Yes, just as you have known, the only recommended way of invoking UI
thread
methods from other threads is using Control.Invoke/BeginInvoke methods, I
know you do not want to use them, but these 2 methods are what .Net
Winform
provided for this purpose.

If you do not want the component user to take care of the cross-thread
Control.Invoke/BeginInvoke requirement, you'd better refer to
System.Timers.Timer class implementation model. System.Timers.Timer class
normally runs Elapsed event in another non-UI thread, however, it provided
a SynchronizingObject to deal with this. Once SynchronizingObject is set
to
certain Control reference, this Elapsed event will be executed in that
control's UI thread without Timer class user aware of. This is very
convinient for the class/component user and I think is what you wanted to
achieve. To achieve this, the Timer class uses MyTimerCallback method to
call the Elapsed event like this:

private void MyTimerCallback(object state)
{
....
try
{
if (this.onIntervalElapsed != null)
{
if ((this.SynchronizingObject != null) &&
this.SynchronizingObject.InvokeRequired)
{

this.SynchronizingObject.BeginInvoke(this.onIntervalElapsed, new object[]
{
this, args1 });
}
else
{
this.onIntervalElapsed(this, args1);
}
}
}
catch (Exception)
{
}
...
}
Then in the Elapsed event, the user can write code does not care of the UI
thread operation issue. You may use this design as well.

Additionally, there is rule regarding not use p/invoke. Actually, as you
have found out, .Net winform internally p/invokes Win32 API to complete
must task. So if you want, you may use p/invoke freely. You may
encapsulate
all the Win32 API declaration in a class for good maintain ability.

Hope this helps.

Best regards,
Jeffrey Tan
Microsoft Online Community Support
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