C# Discussion Boards - CodeProject

2-Jul-02 1:20

how do i get all the treenodes in a treeview including the subdirectories??

treenodecollection = treeview.topnode.nodes return only the child nodes of the topnode and doesnt include the subdirectories.

i = treeview.topnode.getnodecount(true) does return the count but doesnt seem to return the nodecollection as such.

Is there any method available or it has to be implemented recrusively.

thanks.

Re: All treenodes in a treeView

James T. Johnson3-Jul-02 8:58

James T. Johnson

3-Jul-02 8:58

I believe you'll have to loop through the node collection for each node.

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

The C# using operator

Chris Maunder1-Jul-02 15:47

Chris Maunder

1-Jul-02 15:47

I'm just wondering about the C# using operator and what it means in terms of style.

In C# you can either do:

Font font = new Font("Arial", 10.0f);
// use font
...
font.Dispose(); // free resource
// garbage collector will clean up memory

Font font = new Font("Arial", 10.0f);
using (font)
{
    // use font
    ...
}
// compiler automatically calls font.Dispose();
// garbage collector will clean up memory

Has anyone used the using keyword? If so, why? For convenience? Style? For fear that IDisposable may be changed in future releases and using will still work while Dispose may not?

Just curious.

cheers,
Chris Maunder

I spent a minute looking at my own code by accident. I was thinking "What the hell is this guy doing?" - @Logan

Re: The C# using operator

Andy Smith1-Jul-02 16:03

Andy Smith

1-Jul-02 16:03

a using statement written like this:

using( Font font = new Font("Arial", 10.0f) ) {
// use font
}

actually translates to this:

try {
Font font = new Font("Arial", 10.0f) );
// use font
} finally {
if ( font != null ) {
((IDisposable)font).Dispose();
}
}

now i don't know about you...
but i find the "using" method much clearer and easier to read.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:05

Rama Krishna Vavilala

1-Jul-02 16:05

Except that if there is more than 1 resource it gets ugly.

Re: The C# using operator

Chris Maunder1-Jul-02 16:25

Chris Maunder

1-Jul-02 16:25

Excellent point.

It's strange that in C++/SDK code you rarely see developers checking every return code and every HRESULT to ensure that things are going smoothly. I wonder if constructs like using will enourage more developers to be a little more careful.

cheers,
Chris Maunder

I spent a minute looking at my own code by accident. I was thinking "What the hell is this guy doing?" - @Logan

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:03

Rama Krishna Vavilala

1-Jul-02 16:03

I liked it initially but it really gets ugly for nested loops and more than 1 resource. C++ smart types are far better. I prefer to use try {} finally {} now.

Re: The C# using operator

Nish Nishant1-Jul-02 16:08

Nish Nishant

1-Jul-02 16:08

This might be a stupid question. But why call Dispose manually? Isnt that what the GC is for? Or are we talking about freeing GDI resources here?

Nish Confused | :confused:

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: The C# using operator

Andy Smith1-Jul-02 16:12

Andy Smith

1-Jul-02 16:12

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

Re: The C# using operator

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]

Re: The C# using operator

Andy Smith1-Jul-02 17:28

Andy Smith

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.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:17

Rama Krishna Vavilala

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 | :)

Re: The C# using operator

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

Re: The C# using operator

Rama Krishna Vavilala6-Jul-02 16:06

Rama Krishna Vavilala

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.

Re: The C# using operator

Andy Smith1-Jul-02 16:15

Andy Smith

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.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:25

Rama Krishna Vavilala

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.

Re: The C# using operator

Andy Smith1-Jul-02 16:29

Andy Smith

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
}

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:32

Rama Krishna Vavilala

1-Jul-02 16:32

Wow, I never knew that. Frown | :(

Thanks.

But still C++ detructor stuff is far better.

Re: The C# using operator

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

Re: The C# using operator

Andy Smith1-Jul-02 17:30

Andy Smith

1-Jul-02 17:30

oh, ya, thanks for the correction.

still better than the alternative.

Re: The C# using operator

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]

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

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

Andy Smith

2-Jul-02 7:52

your understanding on 1 is incorrect.
the variable may go out of scope at the end of a block, but that does not mean that the GC will immediately collect it. The GC collects memory on its own schedule.

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

leppie3-Jul-02 5:17

leppie

3-Jul-02 5:17

thx, some reading made me understand some more ( i somehow understand MSDN english better than some of the people's posts here Smile | :)

).

to sum it up:

u would only use the using statement when u need to immediately free up resources, if so desired, else the GC will take care of it in its own time.

READ MSDN

Using OpenGL with C#

Ilan Ehrenfeld30-Jun-02 23:51

Ilan Ehrenfeld

30-Jun-02 23:51

Hi!

Can I use OpenGL from C#?

If yse how do I do it? Can I get an example?

Thanks
Ilan Ehrenfeld

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