When I, let's say I'm a form, register myself for an event, I use a syntax
such as:
Class1.EventNam e += new EventNameHandle r(MyFormsEventH andler);
Somewhere in global scope, I have defined the delegate EventNameHandle r:
public delegate void EventNameHandle r(object source, Eventargs e);
In Class1 I have:
public static event EventNameHandle r EventName;
I assume that the event EventName keeps track of all of the EventNameHandle r
delegates that are register with it. But who unregisters the delegate when
my form is destroyed? Can someone please explain?
Regards,
David Rogers
6  2066 
"David Rogers" <dr*****@NOSPAM .fhcrc.org> wrote in message
news:e7******** ******@tk2msftn gp13.phx.gbl... I assume that the event EventName keeps track of all of the
EventNameHandle r delegates that are register with it. But who unregisters the delegate when
my form is destroyed? Can someone please explain?
I wondered about this, and used a heap profiler (.NETProfiler?) to
investigate what was going on. Basically, my forms were not dying until I
explicitly unregistered the delegates!! If you get hold of a heap profiler
(http://www.scitech.se/memprofiler/) you can investigate this yourself. I
supppose it kinda makes sense though, the forms are being referenced by the
delegates (by way of the callback), so the form shouldn't be garbage
collected until there is nothing in memory referencing it. I can't remember
if this is still the case even the delegate is set up between the form and a
control it contains?
Tobin
Regards,
David Rogers
Just to add, if want to unregister the delegate I find the best places for
adding and removing it are:
Control.OnHandl eCreated
and
Control.OnHandl eDestroyed
The Form class derives from Control so you can override them to do your
registering / unregistering.
Regards
Lee
"Jon Skeet" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@news.microsof t.com... David Rogers <dr*****@NOSPAM .fhcrc.org> wrote: When I, let's say I'm a form, register myself for an event, I use a
syntax such as:
Class1.EventNam e += new EventNameHandle r(MyFormsEventH andler);
Somewhere in global scope, I have defined the delegate EventNameHandle r:
public delegate void EventNameHandle r(object source, Eventargs e);
In Class1 I have:
public static event EventNameHandle r EventName;
I assume that the event EventName keeps track of all of the
EventNameHandle r delegates that are register with it. But who unregisters the delegate
when my form is destroyed? Can someone please explain?
Unless you're doing it yourself, I don't believe anything is
unregistering the event. Your form instance will stick around...
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
David Rogers <dr*****@NOSPAM .fhcrc.org> wrote: Related question: Does the framework take care of the event handlers that
are added to controls by the designer? If not, does this mean that my child
form's button click handler is going to cause that form instance to remain
in memory even after the form is gone?
If that is the case, there must be 22 million programs out there that are
leaking memory like a sieve!
Not necessarily - it's only a memory leak if you're adding the delegate
to event *outside* the form itself. Normal forms where, say, clicking a
button triggers a label to change, don't have a memory leak - the whole
lot becomes eligible for garbage collection at the same time.
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
David,
I do not believe in this instance its a problem, as the form has a reference
to the child & the child has a reference to the form. (circular references).
When you get ride of the form only that form references the children so
every thing should go away.
If your other example, form1 had a reference to form2, you had a reference
to form1, which was keeping every thing alive.
Hope this helps
Jay
"David Rogers" <dr*****@NOSPAM .fhcrc.org> wrote in message
news:OR******** *****@TK2MSFTNG P11.phx.gbl... Related question: Does the framework take care of the event handlers that
are added to controls by the designer? If not, does this mean that my
child form's button click handler is going to cause that form instance to remain
in memory even after the form is gone?
If that is the case, there must be 22 million programs out there that are
leaking memory like a sieve!
David
"Lee Alexander" <lee@No_Spam_Pl ease_Digita.com > wrote in message
news:e$******** *******@TK2MSFT NGP11.phx.gbl.. . Just to add, if want to unregister the delegate I find the best places
for adding and removing it are:
Control.OnHandl eCreated
and
Control.OnHandl eDestroyed
The Form class derives from Control so you can override them to do your
registering / unregistering.
Regards
Lee
"Jon Skeet" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@news.microsof t.com... David Rogers <dr*****@NOSPAM .fhcrc.org> wrote:
> When I, let's say I'm a form, register myself for an event, I use a
syntax > such as:
>
> Class1.EventNam e += new EventNameHandle r(MyFormsEventH andler);
>
> Somewhere in global scope, I have defined the delegate EventNameHandle r: >
> public delegate void EventNameHandle r(object source, Eventargs
e); >
> In Class1 I have:
>
> public static event EventNameHandle r EventName;
>
> I assume that the event EventName keeps track of all of the
EventNameHandle r > delegates that are register with it. But who unregisters the
delegate when > my form is destroyed? Can someone please explain?
Unless you're doing it yourself, I don't believe anything is
unregistering the event. Your form instance will stick around...
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
"Jon Skeet" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@news.microsof t.com... David Rogers <dr*****@NOSPAM .fhcrc.org> wrote: Related question: Does the framework take care of the event handlers
that are added to controls by the designer? If not, does this mean that my
child form's button click handler is going to cause that form instance to
remain in memory even after the form is gone?
If that is the case, there must be 22 million programs out there that
are leaking memory like a sieve!
Not necessarily - it's only a memory leak if you're adding the delegate
to event *outside* the form itself. Normal forms where, say, clicking a
button triggers a label to change, don't have a memory leak - the whole
lot becomes eligible for garbage collection at the same time.
[Kind of related comments!...]
That does make sense actually - and saves us a little effort. Still a pain
for me becuase I use a kind of MVC architecture where forms subscribe to
events in 'back end' classes. So, I always have to remember to explicitly
code the unsubscribe when the form is destroyed. Thinking about it, would it
be possible to create a deligate class that could respond to the subscribers
Disposed event? When this is fired, it could remove the object from it's
list of recipients? So then calling Form.Dispose() would automatically
unsubscribe it from any delegates it's referenced by? Does anyone know if
this is possible? I don't even know if you can create custom delegates
though!? Just thinking out loud...
Tobin
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too
Arghhhh! Of course not, the events themselves are destroyed with the form,
so there is no need to unregister the delegate instances that are registered
with those events...
Cheers!
"Jon Skeet" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@news.microsof t.com... David Rogers <dr*****@NOSPAM .fhcrc.org> wrote: Related question: Does the framework take care of the event handlers
that are added to controls by the designer? If not, does this mean that my
child form's button click handler is going to cause that form instance to
remain in memory even after the form is gone?
If that is the case, there must be 22 million programs out there that
are leaking memory like a sieve!
Not necessarily - it's only a memory leak if you're adding the delegate
to event *outside* the form itself. Normal forms where, say, clicking a
button triggers a label to change, don't have a memory leak - the whole
lot becomes eligible for garbage collection at the same time.
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet/
If replying to the group, please do not mail me too This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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