events in multithreaded application

Hi,

I want to create a class that creates a thread internally to do some work.
It will interact with winforms using events.

What happens when the code that is running in a seperate thread raises an
event?
Will the code in the event handler that is attached to the event run in the
internal thread,
or will it run in the GUI thread?

The MSDN documentation says that all interaction with the GUI from other
threads have
to go through an Invoke method.
The user shouldn't know that the class used threads internally.


If anybody has any ideas, article links etc it would be most apreciated.

Thanks,

Chris

Hi Christopher,

> What happens when the code that is running in a seperate thread raises an
> event?
> Will the code in the event handler that is attached to the event run in
the
> internal thread,
> or will it run in the GUI thread?

It will run in the worker thread not in the UI thread.
>
> The MSDN documentation says that all interaction with the GUI from other
> threads have
> to go through an Invoke method.
> The user shouldn't know that the class used threads internally.

You cannot change the UI control form the thread that has not created the
control. But this is only for interacting with the UI controls (forms,
buttons, listboxes, etc). All other objects you can use from within whatever
thread you want as long as you take care of the sychornizations with the
other threads your thread may share serources with.

You can ofcourse understand whether you can tuch UI control directly or you
have to call Invoke. Poll the control's InvokeRequired property and if it is
true that means the call is has been made form thread different form the
thread created the control so control's Invoke method has to be used in
order to swithch the execution in the UI thread.
However, you cannot add control created from one thread to a form or control
created from another (the framework will throw an exception if you try).
Thus, you don't have to check InvokeRequired for all controls you want to
update in the event handler. You can check only with one of them (usually
the form) and call its Invoke method if necessary and then update all
controls you need.

HTH
B\rgds
100

Thanks for the information.

What I really wanted to do was to hide the fact that the class was
multithreaded.
Is there any way to marshall the event so that the class raises the event in
the worker thread,
but the event handler executes in the GUI thread?

The GUI just uses the object, it doesn't care how it is implemented.

Chris


"100" <100@100.com> wrote in message
news:uexSAIF4DHA.1556@TK2MSFTNGP11.phx.gbl...
> Hi Christopher,
>
> > What happens when the code that is running in a seperate thread raises
an
> > event?
> > Will the code in the event handler that is attached to the event run in
> the
> > internal thread,
> > or will it run in the GUI thread?
>
> It will run in the worker thread not in the UI thread.
> >
> > The MSDN documentation says that all interaction with the GUI from other
> > threads have
> > to go through an Invoke method.
> > The user shouldn't know that the class used threads internally.
>
> You cannot change the UI control form the thread that has not created the
> control. But this is only for interacting with the UI controls (forms,
> buttons, listboxes, etc). All other objects you can use from within
whatever
> thread you want as long as you take care of the sychornizations with the
> other threads your thread may share serources with.
>
> You can ofcourse understand whether you can tuch UI control directly or
you
> have to call Invoke. Poll the control's InvokeRequired property and if it
is
> true that means the call is has been made form thread different form the
> thread created the control so control's Invoke method has to be used in
> order to swithch the execution in the UI thread.
> However, you cannot add control created from one thread to a form or
control
> created from another (the framework will throw an exception if you try).
> Thus, you don't have to check InvokeRequired for all controls you want to
> update in the event handler. You can check only with one of them (usually
> the form) and call its Invoke method if necessary and then update all
> controls you need.
>
> HTH
> B\rgds
> 100
>
>

Hi Christopher,
I'm afraid it is not possible unless you have a reference to one of the
controls in the UI thread.

B\rgds
100

"Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in message
news:400ee66f$1@news.broadpark.no...
> Thanks for the information.
>
> What I really wanted to do was to hide the fact that the class was
> multithreaded.
> Is there any way to marshall the event so that the class raises the event
in
> the worker thread,
> but the event handler executes in the GUI thread?
>
> The GUI just uses the object, it doesn't care how it is implemented.
>
> Chris
>
>
> "100" <100@100.com> wrote in message
> news:uexSAIF4DHA.1556@TK2MSFTNGP11.phx.gbl...
> > Hi Christopher,
> >
> > > What happens when the code that is running in a seperate thread raises
> an
> > > event?
> > > Will the code in the event handler that is attached to the event run
in
> > the
> > > internal thread,
> > > or will it run in the GUI thread?
> >
> > It will run in the worker thread not in the UI thread.
> > >
> > > The MSDN documentation says that all interaction with the GUI from
other
> > > threads have
> > > to go through an Invoke method.
> > > The user shouldn't know that the class used threads internally.
> >
> > You cannot change the UI control form the thread that has not created
the
> > control. But this is only for interacting with the UI controls (forms,
> > buttons, listboxes, etc). All other objects you can use from within
> whatever
> > thread you want as long as you take care of the sychornizations with the
> > other threads your thread may share serources with.
> >
> > You can ofcourse understand whether you can tuch UI control directly or
> you
> > have to call Invoke. Poll the control's InvokeRequired property and if
it
> is
> > true that means the call is has been made form thread different form the
> > thread created the control so control's Invoke method has to be used in
> > order to swithch the execution in the UI thread.
> > However, you cannot add control created from one thread to a form or
> control
> > created from another (the framework will throw an exception if you try).
> > Thus, you don't have to check InvokeRequired for all controls you want
to
> > update in the event handler. You can check only with one of them
(usually
> > the form) and call its Invoke method if necessary and then update all
> > controls you need.
> >
> > HTH
> > B\rgds
> > 100
> >
> >
>
>

Well that is just too bad, it would be a nice feature though.
Thanks for the help.

Chris


"100" <100@100.com> wrote in message
news:unWK5NG4DHA.2136@TK2MSFTNGP12.phx.gbl...
> Hi Christopher,
> I'm afraid it is not possible unless you have a reference to one of the
> controls in the UI thread.
>
> B\rgds
> 100
>
> "Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in
message
> news:400ee66f$1@news.broadpark.no...
> > Thanks for the information.
> >
> > What I really wanted to do was to hide the fact that the class was
> > multithreaded.
> > Is there any way to marshall the event so that the class raises the
event
> in
> > the worker thread,
> > but the event handler executes in the GUI thread?
> >
> > The GUI just uses the object, it doesn't care how it is implemented.
> >
> > Chris
> >
> >
> > "100" <100@100.com> wrote in message
> > news:uexSAIF4DHA.1556@TK2MSFTNGP11.phx.gbl...
> > > Hi Christopher,
> > >
> > > > What happens when the code that is running in a seperate thread
raises
> > an
> > > > event?
> > > > Will the code in the event handler that is attached to the event run
> in
> > > the
> > > > internal thread,
> > > > or will it run in the GUI thread?
> > >
> > > It will run in the worker thread not in the UI thread.
> > > >
> > > > The MSDN documentation says that all interaction with the GUI from
> other
> > > > threads have
> > > > to go through an Invoke method.
> > > > The user shouldn't know that the class used threads internally.
> > >
> > > You cannot change the UI control form the thread that has not created
> the
> > > control. But this is only for interacting with the UI controls (forms,
> > > buttons, listboxes, etc). All other objects you can use from within
> > whatever
> > > thread you want as long as you take care of the sychornizations with
the
> > > other threads your thread may share serources with.
> > >
> > > You can ofcourse understand whether you can tuch UI control directly
or
> > you
> > > have to call Invoke. Poll the control's InvokeRequired property and if
> it
> > is
> > > true that means the call is has been made form thread different form
the
> > > thread created the control so control's Invoke method has to be used
in
> > > order to swithch the execution in the UI thread.
> > > However, you cannot add control created from one thread to a form or
> > control
> > > created from another (the framework will throw an exception if you
try).
> > > Thus, you don't have to check InvokeRequired for all controls you want
> to
> > > update in the event handler. You can check only with one of them
> (usually
> > > the form) and call its Invoke method if necessary and then update all
> > > controls you need.
> > >
> > > HTH
> > > B\rgds
> > > 100
> > >
> > >
> >
> >
>
>

Hi Christopher,
You might have more then one UI thread how could you possibly know at which
thread context to execute the event handler. Further more, how I said the
events need to be executed by an UI thread only when the consumer wants to
tuch the UI how can you possibly know what I'm going to do in response to
the event. If all events were to be executed in an UI thread wouldn't it
defeat the idea of multithreading.

B\rgds
100

"Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in message
news:400ef0dc$1@news.broadpark.no...
> Well that is just too bad, it would be a nice feature though.
> Thanks for the help.
>
> Chris
>
>
> "100" <100@100.com> wrote in message
> news:unWK5NG4DHA.2136@TK2MSFTNGP12.phx.gbl...
> > Hi Christopher,
> > I'm afraid it is not possible unless you have a reference to one of the
> > controls in the UI thread.
> >
> > B\rgds
> > 100
> >
> > "Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in
> message
> > news:400ee66f$1@news.broadpark.no...
> > > Thanks for the information.
> > >
> > > What I really wanted to do was to hide the fact that the class was
> > > multithreaded.
> > > Is there any way to marshall the event so that the class raises the
> event
> > in
> > > the worker thread,
> > > but the event handler executes in the GUI thread?
> > >
> > > The GUI just uses the object, it doesn't care how it is implemented.
> > >
> > > Chris
> > >
> > >
> > > "100" <100@100.com> wrote in message
> > > news:uexSAIF4DHA.1556@TK2MSFTNGP11.phx.gbl...
> > > > Hi Christopher,
> > > >
> > > > > What happens when the code that is running in a seperate thread
> raises
> > > an
> > > > > event?
> > > > > Will the code in the event handler that is attached to the event
run
> > in
> > > > the
> > > > > internal thread,
> > > > > or will it run in the GUI thread?
> > > >
> > > > It will run in the worker thread not in the UI thread.
> > > > >
> > > > > The MSDN documentation says that all interaction with the GUI from
> > other
> > > > > threads have
> > > > > to go through an Invoke method.
> > > > > The user shouldn't know that the class used threads internally.
> > > >
> > > > You cannot change the UI control form the thread that has not
created
> > the
> > > > control. But this is only for interacting with the UI controls
(forms,
> > > > buttons, listboxes, etc). All other objects you can use from within
> > > whatever
> > > > thread you want as long as you take care of the sychornizations with
> the
> > > > other threads your thread may share serources with.
> > > >
> > > > You can ofcourse understand whether you can tuch UI control directly
> or
> > > you
> > > > have to call Invoke. Poll the control's InvokeRequired property and
if
> > it
> > > is
> > > > true that means the call is has been made form thread different form
> the
> > > > thread created the control so control's Invoke method has to be used
> in
> > > > order to swithch the execution in the UI thread.
> > > > However, you cannot add control created from one thread to a form or
> > > control
> > > > created from another (the framework will throw an exception if you
> try).
> > > > Thus, you don't have to check InvokeRequired for all controls you
want
> > to
> > > > update in the event handler. You can check only with one of them
> > (usually
> > > > the form) and call its Invoke method if necessary and then update
all
> > > > controls you need.
> > > >
> > > > HTH
> > > > B\rgds
> > > > 100
> > > >
> > > >
> > >
> > >
> >
> >
>
>

I see your point, thanks.

Chris


"100" <100@100.com> wrote in message
news:eyYxHiG4DHA.1936@TK2MSFTNGP12.phx.gbl...
> Hi Christopher,
> You might have more then one UI thread how could you possibly know at
which
> thread context to execute the event handler. Further more, how I said the
> events need to be executed by an UI thread only when the consumer wants to
> tuch the UI how can you possibly know what I'm going to do in response to
> the event. If all events were to be executed in an UI thread wouldn't it
> defeat the idea of multithreading.
>
> B\rgds
> 100
>
> "Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in
message
> news:400ef0dc$1@news.broadpark.no...
> > Well that is just too bad, it would be a nice feature though.
> > Thanks for the help.
> >
> > Chris
> >
> >
> > "100" <100@100.com> wrote in message
> > news:unWK5NG4DHA.2136@TK2MSFTNGP12.phx.gbl...
> > > Hi Christopher,
> > > I'm afraid it is not possible unless you have a reference to one of
the
> > > controls in the UI thread.
> > >
> > > B\rgds
> > > 100
> > >
> > > "Christopher Kimbell" <c_kimbell@REMOVETHISemail.comNOSPAM> wrote in
> > message
> > > news:400ee66f$1@news.broadpark.no...
> > > > Thanks for the information.
> > > >
> > > > What I really wanted to do was to hide the fact that the class was
> > > > multithreaded.
> > > > Is there any way to marshall the event so that the class raises the
> > event
> > > in
> > > > the worker thread,
> > > > but the event handler executes in the GUI thread?
> > > >
> > > > The GUI just uses the object, it doesn't care how it is implemented.
> > > >
> > > > Chris
> > > >
> > > >
> > > > "100" <100@100.com> wrote in message
> > > > news:uexSAIF4DHA.1556@TK2MSFTNGP11.phx.gbl...
> > > > > Hi Christopher,
> > > > >
> > > > > > What happens when the code that is running in a seperate thread
> > raises
> > > > an
> > > > > > event?
> > > > > > Will the code in the event handler that is attached to the event
> run
> > > in
> > > > > the
> > > > > > internal thread,
> > > > > > or will it run in the GUI thread?
> > > > >
> > > > > It will run in the worker thread not in the UI thread.
> > > > > >
> > > > > > The MSDN documentation says that all interaction with the GUI
from
> > > other
> > > > > > threads have
> > > > > > to go through an Invoke method.
> > > > > > The user shouldn't know that the class used threads internally.
> > > > >
> > > > > You cannot change the UI control form the thread that has not
> created
> > > the
> > > > > control. But this is only for interacting with the UI controls
> (forms,
> > > > > buttons, listboxes, etc). All other objects you can use from
within
> > > > whatever
> > > > > thread you want as long as you take care of the sychornizations
with
> > the
> > > > > other threads your thread may share serources with.
> > > > >
> > > > > You can ofcourse understand whether you can tuch UI control
directly
> > or
> > > > you
> > > > > have to call Invoke. Poll the control's InvokeRequired property
and
> if
> > > it
> > > > is
> > > > > true that means the call is has been made form thread different
form
> > the
> > > > > thread created the control so control's Invoke method has to be
used
> > in
> > > > > order to swithch the execution in the UI thread.
> > > > > However, you cannot add control created from one thread to a form
or
> > > > control
> > > > > created from another (the framework will throw an exception if you
> > try).
> > > > > Thus, you don't have to check InvokeRequired for all controls you
> want
> > > to
> > > > > update in the event handler. You can check only with one of them
> > > (usually
> > > > > the form) and call its Invoke method if necessary and then update
> all
> > > > > controls you need.
> > > > >
> > > > > HTH
> > > > > B\rgds
> > > > > 100
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>