A question on threading

[Rahul]

Hello,

I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.

The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).

So, I want the GUI to stay responsive while executing this method.

I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.

How can I keep my window responsive while running this method? Any
ideas?

[Mugunth]

Re: A question on threading

On Mar 2, 8:38 pm, Rahul <rahu...@gmail. comwrote:

Hello,
>
I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.
>
The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).
>
So, I want the GUI to stay responsive while executing this method.
>
I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.
>
How can I keep my window responsive while running this method? Any
ideas?

Try using a backgroundworke r.

[Peter Webb]

Re: A question on threading


"Rahul" <rahuldj@gmail. comwrote in message
news:00d8eb3f-a115-4527-8052-1dc6139b5ab3@e6 g2000prf.google groups.com...

Hello,
>
I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.
>
The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).
>
So, I want the GUI to stay responsive while executing this method.
>
I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.
>
How can I keep my window responsive while running this method? Any
ideas?

Application.DoE vents() will force your thread to process messages from the
UI. Its probably not the right way to do it, but it will very probably work.
Just stick it in somewhere you expect to be called at least 50 times per
second and the UI should work just fine.

[Rahul]

Re: A question on threading

On Mar 2, 4:47 am, Mugunth <mugunth.ku...@ gmail.comwrote:

On Mar 2, 8:38 pm, Rahul <rahu...@gmail. comwrote:
>
>
>

Hello,

>

I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.

>

The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).

>

So, I want the GUI to stay responsive while executing this method.

>

I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.

>

How can I keep my window responsive while running this method? Any
ideas?

>
Try using a backgroundworke r.

I tried to call the function through BackgroundWorke r.

The "this.Invalidat e()" runs properly. But this.Update() (which is the
next statement) does not work.
It throws the same exception "Cross-thread operation not valid:
Control '<FormName>' accessed from a thread other than the thread it
was created on."

this.Update() is necessary to ensure that GUI gets updated quickly, so
as to make the changes visible in pseudo-real-time.

Thanks for the reply.

Any other ideas?

[Rahul]

Re: A question on threading

On Mar 2, 5:10 am, "Peter Webb" <webbfam...@DIE SPAMDIEoptusnet .com.au>
wrote:

"Rahul" <rahu...@gmail. comwrote in message
>
news:00d8eb3f-a115-4527-8052-1dc6139b5ab3@e6 g2000prf.google groups.com...
>
>
>

Hello,

>

I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.

>

The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).

>

So, I want the GUI to stay responsive while executing this method.

>

I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.

>

How can I keep my window responsive while running this method? Any
ideas?

>
Application.DoE vents() will force your thread to process messages from the
UI. Its probably not the right way to do it, but it will very probably work.
Just stick it in somewhere you expect to be called at least 50 times per
second and the UI should work just fine.

Peter,

A brilliant hack!! Although this might not be the best possible way...
it gets the job done.

Unless someone suggests a more "elegant" solution, this would do just
fine.

Thanks a lot! :)

[Alfred Myers]

Re: A question on threading

Hi,

The UI only should be updated by the same thread that created the Control's
windows handle.
To do that, you can use Control.Invoke which receives a delegate pointing to
the code you want to execute.
For the delegate you can use a MethodInvoker such as the following.

this.Invoke(new MethodInvoker(t his.Update));

HTH


"Rahul" <rahuldj@gmail. comwrote in message
news:54ad76e9-add1-4b33-b8d0-f36eae0961a2@s1 9g2000prg.googl egroups.com...

On Mar 2, 5:10 am, "Peter Webb" <webbfam...@DIE SPAMDIEoptusnet .com.au>
wrote:

>"Rahul" <rahu...@gmail. comwrote in message
>>
>news:00d8eb3 f-a115-4527-8052-1dc6139b5ab3@e6 g2000prf.google groups.com...
>>
>>
>>

Hello,

>>

I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.

>>

The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).

>>

So, I want the GUI to stay responsive while executing this method.

>>

I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.

>>

How can I keep my window responsive while running this method? Any
ideas?

>>
>Application.Do Events() will force your thread to process messages from
>the
>UI. Its probably not the right way to do it, but it will very probably
>work.
>Just stick it in somewhere you expect to be called at least 50 times per
>second and the UI should work just fine.

>
Peter,
>
A brilliant hack!! Although this might not be the best possible way...
it gets the job done.
>
Unless someone suggests a more "elegant" solution, this would do just
fine.
>
Thanks a lot! :)

[Peter Duniho]

Re: A question on threading

On Sun, 02 Mar 2008 05:28:01 -0800, Rahul <rahuldj@gmail. comwrote:

[...]

>Application.Do Events() will force your thread to process messages from
>the
>UI. [...]

>
Peter,
>
A brilliant hack!! Although this might not be the best possible way...
it gets the job done.
>
Unless someone suggests a more "elegant" solution, this would do just
fine.

Do NOT accept that advice. It is the worst way to deal with this issue.

As mentioned by others, you can use more appropriate techniques such as
using a BackgroundWorke r in conjunction with the ProgressChanged event, or
simply calling Control.Invoke( ) or Control.BeginIn voke() from your worker
thread to update the UI.

Note also that there's no need to call Control.Update( ) directly if you're
doing things correctly. For a control where you're doing your own
painting, simply calling Invalidate() will have the intended effect, and
of course for other controls, just changing their state will result in the
control itself doing the necessary invalidation.

I've yet to see an application that call Application.DoE vents() that
wasn't just plain broken. I doubt they exist and I'm certain, given your
description, that it's absolutely the wrong way to approach the issue in
your case.

Pete

[Rahul]

Re: A question on threading

On Mar 2, 6:12 am, "Alfred Myers" <alfred_my...@h otmail.comwrote :

Hi,
>
The UI only should be updated by the same thread that created the Control's
windows handle.
To do that, you can use Control.Invoke which receives a delegate pointing to
the code you want to execute.
For the delegate you can use a MethodInvoker such as the following.
>
this.Invoke(new MethodInvoker(t his.Update));
>
HTH
>
"Rahul" <rahu...@gmail. comwrote in message
>
news:54ad76e9-add1-4b33-b8d0-f36eae0961a2@s1 9g2000prg.googl egroups.com...
>

On Mar 2, 5:10 am, "Peter Webb" <webbfam...@DIE SPAMDIEoptusnet .com.au>
wrote:

"Rahul" <rahu...@gmail. comwrote in message

>

>news:00d8eb3 f-a115-4527-8052-1dc6139b5ab3@e6 g2000prf.google groups.com...

>

Hello,

>

I am writing a program related to image compression in C# (GUI
Application). In that I have a "heavy, long running" method which
among other things, calls this.Invalidate (); to make the screen
refresh to display the changes in image during processing.

>

The problem is that, once the program enters this method, the GUI
Window becomes non-responsive (but GUI gets updated regularly due to
this.Invalidate ()).

>

So, I want the GUI to stay responsive while executing this method.

>

I tried running the method in another thread but then I cannot call
this.Invalidate () because "this" is in parent thread, and it throws
error.

>

How can I keep my window responsive while running this method? Any
ideas?

>

Application.DoE vents() will force your thread to process messages from
the
UI. Its probably not the right way to do it, but it will very probably
work.
Just stick it in somewhere you expect to be called at least 50 times per
second and the UI should work just fine.

>

Peter,

>

A brilliant hack!! Although this might not be the best possible way...
it gets the job done.

>

Unless someone suggests a more "elegant" solution, this would do just
fine.

>

Thanks a lot! :)

Hello Alfred,

I will definitely try this approach.

Thanks a lot.