Re: The C# using operator - C# Discussion Boards

Andy Smith1-Jul-02 16:12

1-Jul-02 16:12

the garbage collector is for handling memory, not scares resources like GDI stuff, file locks, and database connections.

Nish Nishant1-Jul-02 17:15

Nish Nishant

1-Jul-02 17:15

Andy Smith wrote:
the garbage collector is for handling memory, not scares resources like GDI stuff, file locks, and database connections.

But even those will eventually get deleted.

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Andy Smith1-Jul-02 17:28

1-Jul-02 17:28

maybe, but not neccessarily before somebody else NEEDS that resource NOW.

GC is designed to handle memory deallocation. It's not really designed to handle database connection management. that's oledb's responsibility, and it would do it much better than any generic garbage collection could.

Rama Krishna Vavilala1-Jul-02 16:17

1-Jul-02 16:17

GC process doesnot call Dispose it only calls Finalize. Dispose is to free resources.

In Finalize you can free only unmanaged resources and not managed resources. So in case of Font this is ok but again it takes time. I prefer to clean up stuff myself.

More important is freeing managed stuff. (I realized this after seeing areecnt thread in DOTNET list).

StreamWriter writes text in buffers. The buffer is a byte array. So in Finalize you can't flush the buffer. So the only place where you can flush the buffer is Dispose/Close. In these cases you need to call Dispose/Close.

May be our resident C# specialist JTJ can add more to it Smile | :)

James T. Johnson1-Jul-02 17:15

James T. Johnson

1-Jul-02 17:15

You pretty much summarized the reason to explicitly call Dispose on objects that implement it Smile | :)

One thing I noticed though; was you said it can make the code ugly if you have multiple objects to call dispose on; you can simplify it; if they are in one block.

Font f = ....;
Brush br = ....;
Bitmap bi = ....;

try
{
  .....
}
finally
{
  f.Dispose();
  br.Dispose();
  bi.Dispose();
}

Could become

using(Font f = ....)
using(Brush br = ....)
using(Bitmap bi = ....)
{
  .....
}

Which is much much cleaner than the mass indentation you would get otherwise. Smile | :)

James
"Java is free - and worth every penny." - Christian Graus

Rama Krishna Vavilala6-Jul-02 16:06

6-Jul-02 16:06

using(Font f = ....)
using(Brush br = ....)
using(Bitmap bi = ....)

This works. But unfortunately, the generated code still has 3 try{}finally{} blocks.

Andy Smith1-Jul-02 16:15

1-Jul-02 16:15

um, could you give me an example of ugliness?

the more resources "used", the more code it autogenerates for you!

the using statement lets you focus on the intent of the code instead of the mundane plumbing.

Rama Krishna Vavilala1-Jul-02 16:25

1-Jul-02 16:25

It's a matter of personal preference

File f1 = null;
File f2 = null;

try
{

}
finally
{
if (f1 != null)
f1.Dispose();

if (f2 != null)
f2.Dispose();
}

using(f1 = new File(..))
{
using(f2 = new File(..))
{
}
}

I prefer the former.

Andy Smith1-Jul-02 16:29

1-Jul-02 16:29

um... you can put both in the same using statement parens.
so it becomes

using(
Font f1 = new File(..),
Font f2 = new File(..)
) {
// do your thang
}

Rama Krishna Vavilala1-Jul-02 16:32

1-Jul-02 16:32

Wow, I never knew that. Frown | :(

Thanks.

But still C++ detructor stuff is far better.

James T. Johnson1-Jul-02 17:25

James T. Johnson

1-Jul-02 17:25

Andy Smith wrote:
using(
Font f1 = new File(..),
Font f2 = new File(..)
) {

Actually you can't quite do that.

If you have multiple variables of the same type it will work, but you need to omit the second "Font"; so it becomes using(Font f1 = new Font(...), f2 = new Font(...)).

If you wish to declare two different types you can do that as well; but you need to use two using statements.

using(Font f1 = new Font(...))
using(FileStream file = new FileStream(...))
{
  ...
}

That's a lot of elipsis Poke tongue | ;-P

James
"Java is free - and worth every penny." - Christian Graus

Andy Smith1-Jul-02 17:30

1-Jul-02 17:30

oh, ya, thanks for the correction.

still better than the alternative.

Re: The C# using operator (stupid question #2)

Nish Nishant1-Jul-02 16:05

Nish Nishant

1-Jul-02 16:05

Gosh! I never knew about this Blush | :O

Thanks Chris Smile | :)

I won't use it. Something un-elegant about it. Maybe it's just me Smile | :)

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

leppie2-Jul-02 7:36

leppie

2-Jul-02 7:36

Hi
I dont even know how to start asking what I want to know. Dead | X|

1. I assume these are only for variables (objects, whatever) that is needed in a global scope. My understanding is that if you declare and create a new object within {} it will be disposed/finalized automatically when the {} ends.
Is my understanding correct?

2. If correct, does the above post refer to disposing/finalizing global variables when they no longer needed, in case they taking up too many resources?

3. Now I'm too confused what the hell I wanted to know Mad | :mad:

I think I'll go read up on it some more. Smile | :)

PS: Can someone perhaps explain with a realworld / code why it should be used and where specifically. Dead | X|

READ MSDN

Re: The C# using operator (stupid question #2)

Andy Smith2-Jul-02 7:52