Problem With Threading Using Separate Class Files

[Doug Thews]

I'm writing some sample threading code, and have already got many examples
working that look a lot similar to the ones mentioned here. What I'm seeing
is that most people put their method that will be run as a thread inside the
overall Form's class, which is OK for examples, but not really what you'd
see in real life.

So, I decided to write a class (called BusinessOperati on) and have
properties & methods in it. Then, I have 1 method in it called
LongRunningBusi nessOp.

So, in my Form UI code I create the thread by instantiating an object of
type BusinessOperati on and then using the fpr to the LongRunningBusi nessOp
to start my thread.

All works well, except when I want to use delegates to update my UI back
from LongRunningBusi nessOp. For whatever reason, by moving the threaded
code outside of the Form, the compiler now says that the method (I call it
UpdateProgressM eter) I point to when creating an instance of the delegate
(not actually defining the delegate), needs to be static. This wasn't the
case before. Problem is, that if I make it static in the Form class, then
it cannot access the controls within the form.

So, what used to work:

public delegate void ProgressDelegat e(string strPercentage);
private void LongRunningBusi nessOp()
{
// Do code
ProgressDelegat e fpr = new ProgressDelegat e(UpdateProgres sMeter);
// More code then call fpr.Invoke to update the status
}

Now yields a compile error (on the statement after the "//Do code" comment)
when I move the method to outside of the Form class and into it's own class
file. Like I said, all works fine if I just stuff this method and delegate
declaration back into the Form class, but that's not what I want to do.

I know it's probably something simple, like semantics, but sometimes the
obvious ones are the hardest to find when you're the closest to them.

Input would be appreciated.

--
Doug Thews
Director, Customer Solutions
D&D Consulting Services
----------------
Visit my Tech Blog at:
http://www.ddconsult.com/blogs/illuminati/

[Jon Skeet [C# MVP]]

Doug Thews <do*******@remo veme.ddconsult. com> wrote:

I'm writing some sample threading code, and have already got many examples
working that look a lot similar to the ones mentioned here. What I'm seeing
is that most people put their method that will be run as a thread inside the
overall Form's class, which is OK for examples, but not really what you'd
see in real life.

So, I decided to write a class (called BusinessOperati on) and have
properties & methods in it. Then, I have 1 method in it called
LongRunningBusi nessOp.

So, in my Form UI code I create the thread by instantiating an object of
type BusinessOperati on and then using the fpr to the LongRunningBusi nessOp
to start my thread.

All works well, except when I want to use delegates to update my UI back
from LongRunningBusi nessOp. For whatever reason, by moving the threaded
code outside of the Form, the compiler now says that the method (I call it
UpdateProgressM eter) I point to when creating an instance of the delegate
(not actually defining the delegate), needs to be static. This wasn't the
case before. Problem is, that if I make it static in the Form class, then
it cannot access the controls within the form.

I suspect you were trying to use

new ProgressDelegat e (MyForm.UpdateP rogressMeter) where MyForm is the
name of the class. Instead, what you need is

new ProgressDelegat e (someFormInstan ce.UpdateProgre ssMeter) where
someFormInstanc e is a reference to the form you want to update.

When you instantiate BusinessOperati on, you need to pass it the form it
"belongs" to so that it knows what to update.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Doug Thews]

That sounds very plausible, and it is what I'm doing. This may be a very
stupid question, but how can I get access to the instance of the running
form when I can't pass anything to the thread that's started? I guess I
could make a public property in the BusinessOperati on class that holds the
value after I instantiate the object, and then reference it from within the
delegate creation. Is this the "standard" way to do it? How would
something like this actually fix a compiler error? Wouldn't the signatures
be detected the same, thus I'd still get the error about not being a static
method?

--
Doug Thews
Director, Customer Solutions
D&D Consulting Services
----------------
Visit my Tech Blog at:
http://www.ddconsult.com/blogs/illuminati/

"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

Doug Thews <do*******@remo veme.ddconsult. com> wrote:

I'm writing some sample threading code, and have already got many
examples
working that look a lot similar to the ones mentioned here. What I'm
seeing
is that most people put their method that will be run as a thread inside
the
overall Form's class, which is OK for examples, but not really what you'd
see in real life.

So, I decided to write a class (called BusinessOperati on) and have
properties & methods in it. Then, I have 1 method in it called
LongRunningBusi nessOp.

So, in my Form UI code I create the thread by instantiating an object of
type BusinessOperati on and then using the fpr to the
LongRunningBusi nessOp
to start my thread.

All works well, except when I want to use delegates to update my UI back
from LongRunningBusi nessOp. For whatever reason, by moving the threaded
code outside of the Form, the compiler now says that the method (I call
it
UpdateProgressM eter) I point to when creating an instance of the delegate
(not actually defining the delegate), needs to be static. This wasn't
the
case before. Problem is, that if I make it static in the Form class,
then
it cannot access the controls within the form.

I suspect you were trying to use

new ProgressDelegat e (MyForm.UpdateP rogressMeter) where MyForm is the
name of the class. Instead, what you need is

new ProgressDelegat e (someFormInstan ce.UpdateProgre ssMeter) where
someFormInstanc e is a reference to the form you want to update.

When you instantiate BusinessOperati on, you need to pass it the form it
"belongs" to so that it knows what to update.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Doug Thews]

BTW ... I did try it and it seemed to work. I saved off a ptr to the form's
class inside my business operation class, and then referenced it within the
create. It's interesting that the method signatures were the same, so I'm
still a little confused on why I got the compiler error (I would've expected
a null reference exception given the problem)

--
Doug Thews
Director, Customer Solutions
D&D Consulting Services
----------------
Visit my Tech Blog at:
http://www.ddconsult.com/blogs/illuminati/

"Doug Thews" <do*******@remo veme.ddconsult. com> wrote in message
news:%2******** ********@TK2MSF TNGP09.phx.gbl. ..

That sounds very plausible, and it is what I'm doing. This may be a very
stupid question, but how can I get access to the instance of the running
form when I can't pass anything to the thread that's started? I guess I
could make a public property in the BusinessOperati on class that holds the
value after I instantiate the object, and then reference it from within
the delegate creation. Is this the "standard" way to do it? How would
something like this actually fix a compiler error? Wouldn't the
signatures be detected the same, thus I'd still get the error about not
being a static method?

--
Doug Thews
Director, Customer Solutions
D&D Consulting Services
----------------
Visit my Tech Blog at:
http://www.ddconsult.com/blogs/illuminati/

"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

Doug Thews <do*******@remo veme.ddconsult. com> wrote:

I'm writing some sample threading code, and have already got many
examples
working that look a lot similar to the ones mentioned here. What I'm
seeing
is that most people put their method that will be run as a thread inside
the
overall Form's class, which is OK for examples, but not really what
you'd
see in real life.

So, I decided to write a class (called BusinessOperati on) and have
properties & methods in it. Then, I have 1 method in it called
LongRunningBusi nessOp.

So, in my Form UI code I create the thread by instantiating an object of
type BusinessOperati on and then using the fpr to the
LongRunningBusi nessOp
to start my thread.

All works well, except when I want to use delegates to update my UI back
from LongRunningBusi nessOp. For whatever reason, by moving the threaded
code outside of the Form, the compiler now says that the method (I call
it
UpdateProgressM eter) I point to when creating an instance of the
delegate
(not actually defining the delegate), needs to be static. This wasn't
the
case before. Problem is, that if I make it static in the Form class,
then
it cannot access the controls within the form.

I suspect you were trying to use

new ProgressDelegat e (MyForm.UpdateP rogressMeter) where MyForm is the
name of the class. Instead, what you need is

new ProgressDelegat e (someFormInstan ce.UpdateProgre ssMeter) where
someFormInstanc e is a reference to the form you want to update.

When you instantiate BusinessOperati on, you need to pass it the form it
"belongs" to so that it knows what to update.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Ravichandran J.V.]

It is not semantics, it is OOPS. Since the method is in another class,
you need to use an object reference to pass its address to the delegate
as below

ProgressDelegat e fpr = new ProgressDelegat e(ob.UpdateProg ressMeter);

where ob is the instance of the class where you have declared the
method.

with regards,
J.V.Ravichandra n
- http://www.geocities.com/
jvravichandran
- http://www.411asp.net/func/search?
qry=Ravichandra n+J.V.&cob=aspn etpro
- http://www.southasianoutlook.com
- http://www.MSDNAA.Net
- http://www.csharphelp.com
- http://www.poetry.com/Publications/
display.asp?ID= P3966388&BN=999 &PN=2
- Or, just search on "J.V.Ravichandr an"
at http://www.Google.com

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[Jon Skeet [C# MVP]]

Doug Thews <do*******@remo veme.ddconsult. com> wrote:

That sounds very plausible, and it is what I'm doing. This may be a very
stupid question, but how can I get access to the instance of the running
form when I can't pass anything to the thread that's started?
See http://www.pobox.com/~skeet/csharp/t...arameters.html
I guess I
could make a public property in the BusinessOperati on class that holds the
value after I instantiate the object, and then reference it from within the
delegate creation. Is this the "standard" way to do it?
Well, there are lots of ways of passing parameters to methods, but
effectively you'll need a reference to the appropriate form
*somewhere*.
How would
something like this actually fix a compiler error? Wouldn't the signatures
be detected the same, thus I'd still get the error about not being a static
method?

No, because you wouldn't be trying to access it as if it *were* a
static method.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Doug Thews <do*******@remo veme.ddconsult. com> wrote:

BTW ... I did try it and it seemed to work. I saved off a ptr to the form's
class inside my business operation class, and then referenced it within the
create. It's interesting that the method signatures were the same, so I'm
still a little confused on why I got the compiler error (I would've expected
a null reference exception given the problem)

Why would you expect a NullReferenceEx ception, if the reference wasn't
null?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Doug Thews]

Great. Thanks for the assistance everyone.

--
Doug Thews
Director, Customer Solutions
D&D Consulting Services
----------------
Visit my Tech Blog at:
http://www.ddconsult.com/blogs/illuminati/

"Ravichandr an J.V." <jv************ @yahoo.com> wrote in message
news:e2******** ******@TK2MSFTN GP12.phx.gbl...

It is not semantics, it is OOPS. Since the method is in another class,
you need to use an object reference to pass its address to the delegate
as below

ProgressDelegat e fpr = new ProgressDelegat e(ob.UpdateProg ressMeter);

where ob is the instance of the class where you have declared the
method.

with regards,
J.V.Ravichandra n
- http://www.geocities.com/
jvravichandran
- http://www.411asp.net/func/search?
qry=Ravichandra n+J.V.&cob=aspn etpro
- http://www.southasianoutlook.com
- http://www.MSDNAA.Net
- http://www.csharphelp.com
- http://www.poetry.com/Publications/
display.asp?ID= P3966388&BN=999 &PN=2
- Or, just search on "J.V.Ravichandr an"
at http://www.Google.com

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Don't just participate in USENET...get rewarded for it!