Finally vs Using

[Fred Chateau]

What are the differences between a "finally" and a "using" block?

Is it still necessary (or advisable) to use "try" and "catch" blocks within
a "using" block?

--
Regards,

Fred Chateau
e-mail: fchateauAtHotel MotelNowDotCom

[Peter Rilling]

I believe they have no relation to each other.

"finally" is used to ensure that code gets executed regardless of whether an
exception occurred or not in a try/catch block. A using statement is just a
shortcut for way of initializing variables that rely on the Dispose method.
When the "using" block finishes, the system will automatically call the
Dispose method on the object.

Your use of each construct is independent of the use of the other one.

"Fred Chateau" <fc******@127.0 .0.1> wrote in message
news:uZ******** ******@TK2MSFTN GP12.phx.gbl...

What are the differences between a "finally" and a "using" block?

Is it still necessary (or advisable) to use "try" and "catch" blocks within a "using" block?

--
Regards,

Fred Chateau
e-mail: fchateauAtHotel MotelNowDotCom

[Ñ©ÔÆÓ¥]

Hi,
you can test a example like this:
the block it may throw a exception to client,when you use using,it may not
handle it and release related resources.but try/catch/finally will handle
and release revant resource success.try it yourself may can understand it .

--
---------ÌÕ×æºé(Ñ©ÔÆÓ¥)------------
MSN:xueyunying@ hotmailcom
http://shanquan.blogone.net
Mail:ta***@gent le.com.cn
·ÖÏí֪ʶ£¬¹²´´¼ ¤Ç飬¹²Í¬³É¾Í
Share Knowledge,Share Vision,Share
Success
"Fred Chateau" <fc******@127.0 .0.1> дÈëÓʼþ
news:uZ******** ******@TK2MSFTN GP12.phx.gbl...

What are the differences between a "finally" and a "using" block?

Is it still necessary (or advisable) to use "try" and "catch" blocks within a "using" block?

--
Regards,

Fred Chateau
e-mail: fchateauAtHotel MotelNowDotCom

[Bruno Jouhier [MVP]]

using (MyResource res = new MyResource())
{
DoSomething(res );
}

if strictly equivalent to:

{
MyResource res = new MyResource();
try
{
DoSomething(res );
}
finally
{
res.Dispose();
}
}

So, my advice is to use the first form rather than the second one. If you do
this, there should be little use for finally, because most of the situations
where you need a finally block should be related to resource disposal and
coded with "using" rather than finally.

Bruno.

"Fred Chateau" <fc******@127.0 .0.1> a écrit dans le message de
news:uZ******** ******@TK2MSFTN GP12.phx.gbl...

What are the differences between a "finally" and a "using" block?

Is it still necessary (or advisable) to use "try" and "catch" blocks within a "using" block?

--
Regards,

Fred Chateau
e-mail: fchateauAtHotel MotelNowDotCom

[Jeffrey Tan[MSFT]]

Hi Fred,

Thanks for posting in this group.
I think Peter's post has tell the main purpose and difference of Finally
and Using.
You still should use "try" and "catch" blocks to handle the exceptions in
your program.
For more details, please refer to the MSDN document:
http://msdn.microsoft.com/library/de...us/cpguide/htm
l/cpconusingfinal lyblock.asp
http://msdn.microsoft.com/library/de...us/csspec/html
/vclrfcsharpspec _8_13.asp
http://msdn.microsoft.com/library/de...us/cpguide/htm
l/cpconusingtryca tchblocktocatch exceptions.asp

Hope this helps,

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

[Jon Skeet [C# MVP]]

Ñ©ÔÆÓ¥ <go*********@ho tmail.com> wrote:

you can test a example like this:
the block it may throw a exception to client,when you use using,it may not
handle it and release related resources.

Yes it will, because that's the whole point of the "using" construct -
it acts as an elegant way of writing a try/finally pair.

--
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]]

Peter Rilling <pe***@nospam.r illing.net> wrote:

I believe they have no relation to each other.

Yes they do. In particular, the C# language specification says that:

<quote>
A using statement of the form

using (R r1 = new R()) {
r1.F();
}

is precisely equivalent to

R r1 = new R();
try {
r1.F();
}
finally {
if (r1 != null) ((IDisposable)r 1).Dispose();
}
</quote>

You can certainly use each construct within the other, but they're not
unrelated. "using" is just a quick way of doing a try/finally pair of
blocks.

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

[Bruno Jouhier [MVP]]

Hi Jon,

You 're right but the code given by the C# specs is a bit misleading:

* The "if (r1 != null)" test is useless because r1 is never null (if "new
R()" fails, it throws an exception but does not return null).

* The try/finally version lacks curly braces around the whole block, to get
the same scoping as the "using" statement on the r1 variable.

Bruno.
"Jon Skeet [C# MVP]" <sk***@pobox.co m> a écrit dans le message de
news:MP******** *************** *@msnews.micros oft.com...

Peter Rilling <pe***@nospam.r illing.net> wrote:

I believe they have no relation to each other.

Yes they do. In particular, the C# language specification says that:

<quote>
A using statement of the form

using (R r1 = new R()) {
r1.F();
}

is precisely equivalent to

R r1 = new R();
try {
r1.F();
}
finally {
if (r1 != null) ((IDisposable)r 1).Dispose();
}
</quote>

You can certainly use each construct within the other, but they're not
unrelated. "using" is just a quick way of doing a try/finally pair of
blocks.

--
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]]

Bruno Jouhier [MVP] <bj******@clu b-internet.fr> wrote:

You 're right but the code given by the C# specs is a bit misleading:

* The "if (r1 != null)" test is useless because r1 is never null (if "new
R()" fails, it throws an exception but does not return null).
Indeed. On the other hand, a different way of acquiring the resource
*may* return null instead of throwing an exception, in which case no
call to Dispose is made. For instance:

using System;

public class Test : IDisposable
{
static void Main()
{
using (Test t = new Test())
{
Console.WriteLi ne ("Got one");
}

using (Test t = GiveMeNull())
{
Console.WriteLi ne ("Not got one");
}
}

static Test GiveMeNull()
{
return null;
}

public void Dispose()
{
Console.WriteLi ne ("Disposing" );
}
}

It would have been better if the example code in the language
specification had included an example of acquiring resources other than
with a constructor.
* The try/finally version lacks curly braces around the whole block, to get
the same scoping as the "using" statement on the r1 variable.

True. This appears to be an actual bug in the spec.

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

[Alvin Bruney]

> I believe they have no relation to each other.
i believe he was talking about
using(x)
{
}
in which case there is a relation.

--
Regards,
Alvin Bruney
Got tidbits? Get it here...
http://tinyurl.com/2bz4t
"Peter Rilling" <pe***@nospam.r illing.net> wrote in message
news:ex******** *****@TK2MSFTNG P11.phx.gbl...

I believe they have no relation to each other.

"finally" is used to ensure that code gets executed regardless of whether an exception occurred or not in a try/catch block. A using statement is just a shortcut for way of initializing variables that rely on the Dispose method. When the "using" block finishes, the system will automatically call the
Dispose method on the object.

Your use of each construct is independent of the use of the other one.

"Fred Chateau" <fc******@127.0 .0.1> wrote in message
news:uZ******** ******@TK2MSFTN GP12.phx.gbl...

What are the differences between a "finally" and a "using" block?

Is it still necessary (or advisable) to use "try" and "catch" blocks

within

a "using" block?

--
Regards,

Fred Chateau
e-mail: fchateauAtHotel MotelNowDotCom