Re: Garbage Collection & Memory Leaks. - C# Discussion Boards

Christian Graus29-Apr-07 0:14

29-Apr-07 0:14

C# is not C++. Your destructor will be called, one day. Maybe before, maybe after your system collapses. To manage resources in C#, you need to call Dispose whenever disposing of any resource.

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

Re: Garbage Collection & Memory Leaks.

coleydog29-Apr-07 5:25

coleydog

29-Apr-07 5:25

I have added a menu item to my Mdi container form which calls GC.GetTotalMemory( true ); and I report the returned value. GC.GetTotalMemory( true ) should force GC and the destructor (Finalize) as appropriate. This happens for all other class instances EXCEPT Forms displayed with the Show() method. (Modal Forms displayed with the ShowDialog method are GC'ed.)

Re: Garbage Collection & Memory Leaks.

Christian Graus29-Apr-07 10:52

Christian Graus

29-Apr-07 10:52

You should never force the GC to run.

All forms, no matter how they are shown, are kept in memory to be shown again if they are reused. It's a waste of time worrying about the memory a form uses, are you using a ZX81 ? Just make sure you call Dispose as appropriate and trust the GC to do it's job.

Re: Garbage Collection & Memory Leaks.

coleydog29-Apr-07 16:36

coleydog

29-Apr-07 16:36

Hi Christian,

Could you please have a look at my reply to CaiX message. No I am not using ZX81, however the client is using Citrix with some 150 user base so memory usage does impact server utilisation.

Also, how a form is shown does impact.

ShowDialog() does GC the form. (and only the internal Finalize() method calls Dispose as Dispose(false)

whereas

Show() automatically calls Dispose(true) on Close and never GC's the form.

Re: Garbage Collection & Memory Leaks.

Christian Graus29-Apr-07 18:15

Christian Graus

29-Apr-07 18:15

OK, sounds like you're learning a lot about how the GC works. So, make your forms member variables, which is the only half reasonable way to create forms you call Show on, anyhow. Then, recycle the same form, instead of creating them all the time.

Re: Garbage Collection & Memory Leaks.

coleydog29-Apr-07 22:56

coleydog

29-Apr-07 22:56

Thanks for your help.

I believe I've sorted the problem.

If I minimize and maximize the main mdi form the Task Manager reports a low resized memory. So the GC really only works when it needs too and if there is no memory pressure it just lets the app grow. Thanks.

Re: Garbage Collection & Memory Leaks.

caix29-Apr-07 14:11

caix

29-Apr-07 14:11

For most variables if you declare them in a function:

private void DoSomething()
{
MyClass yada;

yada = new MyClass();
}

Then yada gets garbage collected at the end of the function.
But if we do:
private void DoSomething()
{
Form2 yada;

yada = new Form2();
yada.Show();
}

Then yada doesn't get GC.
As Christian says, Dispose() will set it ready for GC, but it will take its own sweet time.
However do you really need to keep creating this form again and again, can't you declare it as an object in you main class, that you just show/hide when you need it. That will stop the memory allocation each time.

Re: Garbage Collection & Memory Leaks.

coleydog29-Apr-07 16:19

coleydog

29-Apr-07 16:19

No, what I'm saying is this -

private void DoSomething()
{
(new Form2()).Show();
}
When Form2 is Closed (user action) Dispose(true) is automatically called by the CLR.

All fine. But after calls to GC.Collect() or GC.GetTotalMemory(true) (both of which should force GC) the form (plus all the controls for the form are never GC'd)

However,

private void DoSomething()
{
(new Form2()).ShowDialog();
}

When Form2 is Closed (user action) Dispose(true) is NOT automatically called by the CLR and shortly after, typically when further memory allocations are required the form gets CG'd.

My point is then that (new Form2()).Show(); requires that a reference to the form be promoted somewhere within the CLR (or O/S) to keep track of the form as the DoSomething() method completes immediately. The internal reference to the form is never removed, even when the form is closed (only when the app terminates) so the form (and all of the form's controls) can never be GC'd.

The typical base managed heap allocation for a complex form instance (multiple pages, multiple controls) appears to be around 1 to 2 megabytes (not including data) which remains after the form is Disposed. The application (an Mdi ERP solution) has around 500 forms and has a user base of around 150 users within the client organisation. The client decision to distribute the solution through Citrix is directly impacted by the cumulative effect of additional memory usage over 20 to 30 users on a typical Citrix server box.

So if no way can be found to force the CLR (or O/S) to relinquish the reference to the form after it is closed and therefore eventually be GC'd then the client decision to distribute the solution through Citrix will need to be seriously re-evaluated.

(Not the case for ShowDialog() which does not terminate the DoSomething() method until the form is Closed()) (therefore no promotion is necessary)

Re: Garbage Collection & Memory Leaks.

Dave Kreskowiak29-Apr-07 16:55

Dave Kreskowiak

29-Apr-07 16:55

Instead of pounding on people to tell you something about your code, that they've never seen, why not test it out and beat on it until you get it to fail, or you manage to see that the GC does know what it's doing. The GC doesn't HAVE to collect objects if it doesn't see the need to, or, more precisely, it doesn't have to release managed memory back to Windows unless Windows wants it back.

If an object is collected, the memory goes back to the managed heap, not back to Windows!

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007

How to get Status of Process (Urgent)

Sanjib Raj28-Apr-07 22:18

Sanjib Raj

28-Apr-07 22:18

how to get status of process for checking if the process status is running or not.

Sanjit.rajbanshi@wlinktech.com

Re: How to get Status of Process (Urgent)

Amir Jalaly29-Apr-07 1:51

Amir Jalaly

29-Apr-07 1:51

Class
System.Diagnostics.Process
Can Help U.
by methods GetProcessesbyName & GetProcesses u can find a process
then by Process Properties Like HasExited u can find is running or some necessary information about process.

Regards Amir Jalaly

MVC custom control

alex.barylski28-Apr-07 20:22

alex.barylski

28-Apr-07 20:22

I want to develope a control following strict MVC principles. My experience in developing custom controls using MFC goes against my current understanding of formal MVC. I realize they are patterns which are meant to be interpreted, but MFC controls seem to have tight coupling of components in the MVC triad.

For instance, if I were to develop a custom control I would likely superclass from a CView (or some other superclass). That CView acts as both the controller and the view, and sometimes has a model as a composite.

I dislike that design and I think proper MVC implementation would reduce concrete depencies.

I have considered how this could be done in straight C and the Windows SDK - later wrapping the control in a CView storing the component in a DLL or similar - Like that editor already on here.

My question is:

If I choose to support Windows only and figure I'll take a stab at C# is implementing a custom control using a strict MVC implementation possible? Do we have any articles on here about using C# with just the SDK to get around restrictions set by frameworks?

Cheers Smile | :)

I'm finding the only constant in software development is change it self.

Re: MVC custom control

Christian Graus28-Apr-07 21:38

Christian Graus

28-Apr-07 21:38

At the end of the day, a control will always be both view, and controller. I've done MVC in C#, but I didn't use the keyboard, I used custom input devices which I was able to write into controller classes, and decouple those from the view. But, as soon as I needed keyboard support, I had to code it into the controls, because, on windows, the controls get the keyboard input.

Re: MVC custom control

alex.barylski29-Apr-07 7:41

alex.barylski

29-Apr-07 7:41

I see what your saying, but I still find frameworks (MFC) non-conforming.

What i was thinking is developing the control using plain SDK (no framework) thus allowing me to keep strict seperation of all three components.

The controller would handle requests (via message pump) and invoke appropriate handlers which in turn would invoke the required models and update view(s).

Then I figured I could just wrap the DLL control as a CView. Obviously the control's API would expose many of the methods in the controller, model and view.

Is doing something like this possible in C#? Know of any articles on CP?

I'm finding the only constant in software development is change it self.

Re: MVC custom control

Christian Graus29-Apr-07 11:02

Christian Graus

29-Apr-07 11:02

Hockey wrote:
but I still find frameworks (MFC) non-conforming

To the assumption that MVC must be followed ? Yes. I used MVC because I knew that there would be 4 or 5 controllers and at least two views. In that sense, it made perfect sense, and worked really well. I doubt that MVC would have improved any of the MFC projects I ever worked on.

Hockey wrote:
Is doing something like this possible in C#?

Not really, no. And, it's barely possible in C. I mean, like I said, it's still your control that recieves your keyboard and mouse messages. If you do it via a message pump, you make intercept a message with a window handle, so you know where it came from, but I still think it's a bit messy.

overlaying image on a video file

enamulhoque28-Apr-07 19:27

enamulhoque

28-Apr-07 19:27

hello all.

I need an algorithm that will take a .avi video file and .jpg image file as input. and the output will be the .avi file with the given image overlayed on it.

can anyone help me to find a solution.

Thanks in advance.

Enamul Hoque

Re: overlaying image on a video file

Christian Graus28-Apr-07 21:39

Christian Graus

28-Apr-07 21:39

It's not an algorithm that you need. Basically, you can do this with DirectX, by creating a filter that superimposes the JPG. Or you can use WPF. Or you can decompose the AVI to frames, merge them with the JPEG, and render a new AVI.

Re: overlaying image on a video file

enamulhoque29-Apr-07 4:27

enamulhoque

29-Apr-07 4:27

Dear Christian,

thanks for your reply.can you explain it in more details kindly?

actually i am working with a C# program. here input will be a .avi file and a .jpg file, and the output is the .avi file with the image overlayed on it.

can i use directX or WPF in C#.

Please mention any article if you know.

Thanks again.

Enamul

Re: overlaying image on a video file

Christian Graus29-Apr-07 10:51

Christian Graus

29-Apr-07 10:51

If you use WPF, you need to rewrite your app to use it. Yes, you should be able to do this in DX, but I've not done it, I am only aware that it can be done.

I know of a component that will do it for you, it costs $800. Is this an option for you ?

Unsafe code

xibeifeijian28-Apr-07 15:54

xibeifeijian

28-Apr-07 15:54

Just look this test method:

public unsafe void Test()
{
int x=23;
int* px=&x;
*px+=1;
Console.Write(*px);
}

I want to know when will x and px distory? D'Oh! | :doh: