Dispose or not??

[qrli]

I used to think that all objects that implement
IDisposable should be disposed. But I found 80% of the
classes implement IDisposable.

But when I looked into the samples, most objects are not
disposed. Generally, they're Gdi objects, form controls,
most components, etc.

So why? How can I decide to dispose or not?

[Champika Nirosh]

Hi,

In most cases you don't have to call dispose method explicitly. The garbage
collector will dispose all unreachable object without puasing the interface.
C# GC manages them well, so most of these sample, you have refered have let
GC to mange it.

Nirosh.

"qrli" <an*******@disc ussions.microso ft.com> wrote in message
news:04******** *************** *****@phx.gbl.. .

I used to think that all objects that implement
IDisposable should be disposed. But I found 80% of the
classes implement IDisposable.

But when I looked into the samples, most objects are not
disposed. Generally, they're Gdi objects, form controls,
most components, etc.

So why? How can I decide to dispose or not?

[Vijaye Raji]

Unless an object's class asks you to explicitly call Dispose, you don't have
to. The GC will take care.

Most GDI objects require you to call Dispose - to release their handle
internally.

vJ

"qrli" <an*******@disc ussions.microso ft.com> wrote in message
news:04******** *************** *****@phx.gbl.. .

I used to think that all objects that implement
IDisposable should be disposed. But I found 80% of the
classes implement IDisposable.

But when I looked into the samples, most objects are not
disposed. Generally, they're Gdi objects, form controls,
most components, etc.

So why? How can I decide to dispose or not?

[Jon Skeet [C# MVP]]

qrli <an*******@disc ussions.microso ft.com> wrote:

I used to think that all objects that implement
IDisposable should be disposed. But I found 80% of the
classes implement IDisposable.
80%? Where do you get that figure? That sounds awfully high to me.
But when I looked into the samples, most objects are not
disposed. Generally, they're Gdi objects, form controls,
most components, etc.
Form controls will usually be disposed by the default code created by
VS.NET.
So why? How can I decide to dispose or not?

I would encourage you to always make sure you dispose of objects which
implement IDisposable.

--
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]]

Champika Nirosh <cn*****@textce ntric.lk> wrote:

In most cases you don't have to call dispose method explicitly. The garbage
collector will dispose all unreachable object without puasing the interface.
C# GC manages them well, so most of these sample, you have refered have let
GC to mange it.

That's a bad idea though, as most types which implement IDisposable
either contain other IDisposables or directly contain native system
resources. Leaving those to the garbage collector (which only knows
about memory pressure, not Windows handle pressure etc) is a bad idea.

--
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]]

Vijaye Raji <no************ @hotmail.com> wrote:

Unless an object's class asks you to explicitly call Dispose, you don't have
to. The GC will take care.

The GC will do it at *some* point, but the very fact that a type
implements IDisposable means it's telling you that it would be
preferable to call Dispose explicitly.

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

Most classes in the following namespaces implement
IDisposable. And they're what I use most.
System.Componen tModel
System.Drawing
System.Windows. Forms

The code VS.NET generated doesn't dispose any thing
except Timer and ImageList. Only Timer and ImageList,
that is those have a constructor take an IContainer
parameter, are added to the components field and are
disposed in the Form.Dispose(bo ol).

-----Original Message-----
qrli <an*******@disc ussions.microso ft.com> wrote:

I used to think that all objects that implement
IDisposable should be disposed. But I found 80% of the
classes implement IDisposable.
80%? Where do you get that figure? That sounds awfully

high to me.

But when I looked into the samples, most objects are not disposed. Generally, they're Gdi objects, form controls, most components, etc.
Form controls will usually be disposed by the default

code created byVS.NET.

So why? How can I decide to dispose or not?
I would encourage you to always make sure you dispose of

objects whichimplement IDisposable.

--
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]]

<an*******@disc ussions.microso ft.com> wrote:

Most classes in the following namespaces implement
IDisposable. And they're what I use most.
System.Componen tModel
System.Drawing
System.Windows. Forms
They may be what you use most when doing GUI stuff, but that's very
different from 80% of classes implementing IDisposable.
The code VS.NET generated doesn't dispose any thing
except Timer and ImageList. Only Timer and ImageList,
that is those have a constructor take an IContainer
parameter, are added to the components field and are
disposed in the Form.Dispose(bo ol).

It *does* dispose things - just not where you can see them. To
demonstrate this, create a simple form with just a label in it. Go into
the code and change it from creating a label to creating a MyLabel, and
define the MyLabel class as:

class MyLabel : Label
{
protected override void Dispose(bool disposing)
{
MessageBox.Show ("Disposing: "+disposing );
base.Dispose (disposing);
}
}

Run it, and close the form - you'll see a message box saying
"Disposing: true" which shows that Dispose has been called.

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

[qrli]

That just proves that all objects are disposed when the
program shut down.

I can give you another example. In the D3D9 Wizard
generated code, D3DSettingForm was created and there's no
Dispose call.

It *does* dispose things - just not where you can see them. Todemonstrate this, create a simple form with just a label in it. Go intothe code and change it from creating a label to creating a MyLabel, anddefine the MyLabel class as:

class MyLabel : Label
{
protected override void Dispose(bool disposing)
{
MessageBox.Show ("Disposing: "+disposing );
base.Dispose (disposing);
}
}

Run it, and close the form - you'll see a message box saying"Disposing: true" which shows that Dispose has been called.
--
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]]

qrli <an*******@disc ussions.microso ft.com> wrote:

That just proves that all objects are disposed when the
program shut down.
No - it's when the form itself is disposed (which it is automatically
on closing). To verify this, you could also do:

new Form1().Dispose (); // Or whatever your form is called

- and again, Dispose is called on all the controls added to it.
I can give you another example. In the D3D9 Wizard
generated code, D3DSettingForm was created and there's no
Dispose call.

Does D3DSettingsForm definitely not call Dispose internally when it's
closed though? I don't have the Managed DirectX SDK installed, but I
suspect it works the same way as the normal System.Windows. Forms does.

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