Passing a Derived Object as a Reference Parameter

[Bruce]

How can I create a method that will take any object derived from a
base class as a reference parameter?

Something like this:

void DestroyObject(r ef BaseObject obj)
{
obj.Dispose();
obj = null;
}

DestroyObject(r ef derivedObject1) ;
DestroyObject(r ef derivedObject2) ;
DestroyObject(r ef derivedObject3) ;

Where derivedObject1, 2 and 3 are of a class type derived from
BaseObject?

Thanks....

--Bruce

[Joanna Carter \(TeamB\)]

Re: Passing a Derived Object as a Reference Parameter

"Bruce" <bvanderw-news5021@mailbl ocks.com > a écrit dans le message de news:
lr4b419mcdou87v 1hq9a495isurs92 brf7@4ax.com...
[color=blue]
> Something like this:
>
> void DestroyObject(r ef BaseObject obj)
> {
> obj.Dispose();
> obj = null;
> }
>
> DestroyObject(r ef derivedObject1) ;
> DestroyObject(r ef derivedObject2) ;
> DestroyObject(r ef derivedObject3) ;[/color]

Yes, but I have to ask why you are explicitly disposing of objects instead
of letting the garbage collector do its work ? Or do your classes hold
references to Windows resources or file handles?

Joanna

--
Joanna Carter
Consultant Software Engineer

[Joanna Carter \(TeamB\)]

Re: Passing a Derived Object as a Reference Parameter

"Bruce" <bvanderw-news5021@mailbl ocks.com > a écrit dans le message de news:
lr4b419mcdou87v 1hq9a495isurs92 brf7@4ax.com...
[color=blue]
> Something like this:
>
> void DestroyObject(r ef BaseObject obj)
> {
> obj.Dispose();
> obj = null;
> }
>
> DestroyObject(r ef derivedObject1) ;
> DestroyObject(r ef derivedObject2) ;
> DestroyObject(r ef derivedObject3) ;[/color]

Yes, but I have to ask why you are explicitly disposing of objects instead
of letting the garbage collector do its work ? Or do your classes hold
references to Windows resources or file handles?

Joanna

--
Joanna Carter
Consultant Software Engineer

[Mattias Sjögren]

Re: Passing a Derived Object as a Reference Parameter

>Where derivedObject1, 2 and 3 are of a class type derived from[color=blue]
>BaseObject?[/color]

BaseObject bo = derivedObject1;
DestroyObject(r ef bo);

But I don't understand why you use a ref parameter. If you used a by
value parameter, you could pass in derivedObject1 directly.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Mattias Sjögren]

Re: Passing a Derived Object as a Reference Parameter

>Where derivedObject1, 2 and 3 are of a class type derived from[color=blue]
>BaseObject?[/color]

BaseObject bo = derivedObject1;
DestroyObject(r ef bo);

But I don't understand why you use a ref parameter. If you used a by
value parameter, you could pass in derivedObject1 directly.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Richard Blewett [DevelopMentor]]

Re: Passing a Derived Object as a Reference Parameter

Dispose doesn't clean up the same resources as the GC. Its there to allow timely clean up of *non-memory* resources. The GC only cleans up memory. If an object implements IDisposable and you have ownership of the object then you should call dispose on it. You are confusing GC with finalization. Finalization is something that happens (hopefully) after the GC realizes a finalizable object is collectable.I say hopefully because it isn't guaranteed to run. You need to make your object finalizable (implement a C# destructor) if and only if you are managing non-managed resrouces like windows HANDLEs and the like. If you implement a finalizer then you should also implement IDisposable. However, there are good reasons to implement IDisposable even if you don;t imeplement a finalizere (for example you have memebers which themselves implement IDisposable).

Regards

Richard Blewett - DevelopMentor

http://www.dotnetconsult.co.uk/weblog

http://www.dotnetconsult.co.uk

"Bruce" <bvanderw-news5021@mailbl ocks.com > a ?crit dans le message de news:
lr4b419mcdou87v 1hq9a495isurs92 brf7@4ax.com...
[color=blue]
> Something like this:
>
> void DestroyObject(r ef BaseObject obj)
> {
> obj.Dispose();
> obj = null;
> }
>
> DestroyObject(r ef derivedObject1) ;
> DestroyObject(r ef derivedObject2) ;
> DestroyObject(r ef derivedObject3) ;[/color]

Yes, but I have to ask why you are explicitly disposing of objects instead
of letting the garbage collector do its work ? Or do your classes hold
references to Windows resources or file handles?

Joanna

[Richard Blewett [DevelopMentor]]

Re: Passing a Derived Object as a Reference Parameter

Dispose doesn't clean up the same resources as the GC. Its there to allow timely clean up of *non-memory* resources. The GC only cleans up memory. If an object implements IDisposable and you have ownership of the object then you should call dispose on it. You are confusing GC with finalization. Finalization is something that happens (hopefully) after the GC realizes a finalizable object is collectable.I say hopefully because it isn't guaranteed to run. You need to make your object finalizable (implement a C# destructor) if and only if you are managing non-managed resrouces like windows HANDLEs and the like. If you implement a finalizer then you should also implement IDisposable. However, there are good reasons to implement IDisposable even if you don;t imeplement a finalizere (for example you have memebers which themselves implement IDisposable).

Regards

Richard Blewett - DevelopMentor

http://www.dotnetconsult.co.uk/weblog

http://www.dotnetconsult.co.uk

"Bruce" <bvanderw-news5021@mailbl ocks.com > a ?crit dans le message de news:
lr4b419mcdou87v 1hq9a495isurs92 brf7@4ax.com...
[color=blue]
> Something like this:
>
> void DestroyObject(r ef BaseObject obj)
> {
> obj.Dispose();
> obj = null;
> }
>
> DestroyObject(r ef derivedObject1) ;
> DestroyObject(r ef derivedObject2) ;
> DestroyObject(r ef derivedObject3) ;[/color]

Yes, but I have to ask why you are explicitly disposing of objects instead
of letting the garbage collector do its work ? Or do your classes hold
references to Windows resources or file handles?

Joanna

[Jon Skeet [C# MVP]]

Re: Passing a Derived Object as a Reference Parameter

Mattias Sjögren <mattias.dont.w ant.spam@mvps.o rg> wrote:[color=blue][color=green]
> >Where derivedObject1, 2 and 3 are of a class type derived from
> >BaseObject?[/color]
>
> BaseObject bo = derivedObject1;
> DestroyObject(r ef bo);
>
> But I don't understand why you use a ref parameter. If you used a by
> value parameter, you could pass in derivedObject1 directly.[/color]

I suspect the point is that the variable will be set to null
afterwards. I can't say it's a pattern I really like though...

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Re: Passing a Derived Object as a Reference Parameter

Mattias Sjögren <mattias.dont.w ant.spam@mvps.o rg> wrote:[color=blue][color=green]
> >Where derivedObject1, 2 and 3 are of a class type derived from
> >BaseObject?[/color]
>
> BaseObject bo = derivedObject1;
> DestroyObject(r ef bo);
>
> But I don't understand why you use a ref parameter. If you used a by
> value parameter, you could pass in derivedObject1 directly.[/color]

I suspect the point is that the variable will be set to null
afterwards. I can't say it's a pattern I really like though...

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Joanna Carter \(TeamB\)]

Re: Passing a Derived Object as a Reference Parameter

"Richard Blewett [DevelopMentor]" <richardb@NOSPA Mdevelop.com> a écrit dans
le message de news: #R5#DglMFHA.314 4@TK2MSFTNGP10. phx.gbl...
[color=blue]
> Dispose doesn't clean up the same resources as the GC.[/color]

That was what I was trying to say in the last sentence of my post; you just
said it better :-))

Joanna

--
Joanna Carter
Consultant Software Engineer