Simple app....silly question?

[David Bonnell]

I have a Windows Forms app that is intended to launch via the SendTo
feature. I want it to perform work (in the background) while updating
a progress bar in the main window.

The problem: I want this to run without any user interaction (except
for launching the app via SendTo).
The form is created via an Application.Run (new myForm()) call, which
then proceeds through the form constructor.

When the constructor returns and the form is displayed, I have no way
of instructing the application to "begin" work. As a workaround, I
temporarily placed a button on the form for the user to initiate work.

I must be missing something. This seems like it would be trivial to
implement. I was considering using a timer as a hack, but surely
there is a better option. Launching a worker thread before exiting
the constructor doesn't strike me as a very good idea either...

Any ideas?

[Peter Duniho]

Re: Simple app....silly question?

On Wed, 29 Oct 2008 11:01:25 -0700, David Bonnell <dbonnell@gmail .com>
wrote:

I have a Windows Forms app that is intended to launch via the SendTo
feature. I want it to perform work (in the background) while updating
a progress bar in the main window.
>
[...]
I must be missing something. This seems like it would be trivial to
implement. I was considering using a timer as a hack, but surely
there is a better option. Launching a worker thread before exiting
the constructor doesn't strike me as a very good idea either...
>
Any ideas?

I'm not sure I understand the question. Do you not want the form to
display at all? Or do you simply want things to happen while the form is
displayed without the user having to specifically interact with the form?

If the latter, then I don't see what your objection to starting a worker
thread in the constructor is -- that should work fine -- but if you don't
like that, you could instead do something similar in the form's OnLoad()
or OnShown() method. You'll definitely want to use a worker thread of
_some_ form, such as BackgroundWorke r, to ensure that the UI remains
responsive.

Pete

[David Bonnell]

Re: Simple app....silly question?

>

I'm not sure I understand the question.  Do you not want the form to  
display at all?  Or do you simply want things to happen while the form is  
displayed without the user having to specifically interact with the form?
>

I want the form to display (the form should consist of only a progress
bar and possibly a status label).
As work is being done (some file manipulation), I want the progress
bar to update to give the user some feedback that the task is being
completed.
Once the task is complete, I want the application to exit.

If the latter, then I don't see what your objection to starting a worker  
thread in the constructor is -- that should work fine -- but if you don't 
like that, you could instead do something similar in the form's OnLoad()  
or OnShown() method.  

I guess I'm not a fan of doing too much in a constructor. Probably
more a lack of understanding than anything...
OnLoad/Shown seems like a good idea. I'll give it a try and see what
shakes loose.

Thanks,
Dave

[Peter Duniho]

Re: Simple app....silly question?

On Wed, 29 Oct 2008 11:40:52 -0700, David Bonnell <dbonnell@gmail .com>
wrote:

[...]
I guess I'm not a fan of doing too much in a constructor. Probably
more a lack of understanding than anything...
OnLoad/Shown seems like a good idea. I'll give it a try and see what
shakes loose.

The only argument I can think of against initializing the worker thread in
the constructor is that if the worker thread should get to a point where
it wants to update the UI before the form has actually gotten a chance to
be fully initialized, then the call to Invoke() (whether explicit in your
code or implicit via a BackgroundWorke r or similar) could fail in the
worker thread.

I suppose that might be a consideration here. It depends on how you
implement the worker thread. But from a more general point of view, as
long as you're not doing something that will lead to an illegal operation,
I don't think that it's necessarily a bad thing to put initialization code
in the constructor. It has to run _sometime_, and the constructor is in
fact a place where things are supposed to get initialized. :)

But, OnShown() should work fine...it's pretty much the latest method/event
that gets called/raised as the form is being created and run, other than
OnPaint() (which would be a silly place to put initialization :) ).

Pete

[David Bonnell]

Re: Simple app....silly question?

>

I suppose that might be a consideration here.  It depends on how you  
implement the worker thread.  But from a more general point of view, as 
long as you're not doing something that will lead to an illegal operation,  
I don't think that it's necessarily a bad thing to put initialization code  
in the constructor.  It has to run _sometime_, and the constructor is in  
fact a place where things are supposed to get initialized.  :)

OnShown worked like a charm. Thanks for the help.

I suspect that in this case it would work fine in the
constructor...b ut I am my own worst enemy. A month from now I'd
probably add more initialization to the constructor and miss some GUI
updates from the worker thread as a result.

Dave