Why use "finally"

[Joe Thompson]

Hi,

This is probably a simple question but I'm curious. What is the purpose of
the "finally" statement? There must be a good reason to use it that I'm just
not getting...

How is this:

method1
{
try
{
x;
}
catch
{
y;
}
finally
{
z;
}
}

different than:

method1
{
try
{
x;
}
catch
{
y;
}

z;
}

Thank you,
Joe

[Marina]

Often, there will be return statements either in the Try or the Catch, or
both. Putting this code in the finally guarantees that it will be executed
in any case. Where as otherwise, you would have to put a copy of it in the
Try and Catch right before the return.

"Joe Thompson" <Jo*********@di scussions.micro soft.com> wrote in message
news:6D******** *************** ***********@mic rosoft.com...

Hi,

This is probably a simple question but I'm curious. What is the purpose
of
the "finally" statement? There must be a good reason to use it that I'm
just
not getting...

How is this:

method1
{
try
{
x;
}
catch
{
y;
}
finally
{
z;
}
}

different than:

method1
{
try
{
x;
}
catch
{
y;
}

z;
}

Thank you,
Joe

[Manohar Kamath]

To release objects that you might have in the try block. The following
article on MSDN probably best explains it:

http://msdn.microsoft.com/library/de...ogether_PG.asp

--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com
"Joe Thompson" <Jo*********@di scussions.micro soft.com> wrote in message
news:6D******** *************** ***********@mic rosoft.com...

Hi,

This is probably a simple question but I'm curious. What is the purpose of the "finally" statement? There must be a good reason to use it that I'm just not getting...

How is this:

method1
{
try
{
x;
}
catch
{
y;
}
finally
{
z;
}
}

different than:

method1
{
try
{
x;
}
catch
{
y;
}

z;
}

Thank you,
Joe

[Bruce Wood]

The answer is that in your second example, "z" is not guaranteed to be
executed, whereas in your first example, it is.

One caveat, though. Your specific examples were a bit unrealistic: it's
bad style to simply have a "catch" without saying what to catch, a
"catch-all" if you'll pardon the pun. So the way that your examples are
written, the only way that "z" will not be executed in the second
example is if "y" throws an exception (inside the catch block).

A more realistic case would be one in which the "catch" blocks catch
specific exceptions, in which case you need "finaly" in case some other
kind of exception that you're not catching occurs.

Sometimes people (like me) even use "finally" with no "catch" at all:
we want the exceptions to percolate up to the caller, but we have to be
sure to release some resource, reset some value, or change some setting
before leaving.

In my code, changing the cursor to an hourglass is a good example:

// Change the cursor to an hourglass
try
{
.... do a long, slow, complicated operation...
}
finally
{
// Change the cursor back to the default
}

I change the cursor back to a default in the finally block because I
want that to happen _even if_ the complex operation inside the "try"
blows up. In fact, the operation is complex enough that it has already
blown up on me several times for reasons beyond my control. If my
"Change the cursor back" code weren't within the "finally" then my
cursor would be stuck as an hourglass.

[Joe Thompson]

Hi Manohar,

Thanks for the reply. I read the article but I still don't see the
difference. Maybe if the example actually showed a resource being released
instead of a Console.WriteLi ne it would be easier to understand...

Joe

"Manohar Kamath" wrote:

To release objects that you might have in the try block. The following
article on MSDN probably best explains it:

http://msdn.microsoft.com/library/de...ogether_PG.asp

--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com
"Joe Thompson" <Jo*********@di scussions.micro soft.com> wrote in message
news:6D******** *************** ***********@mic rosoft.com...

Hi,

This is probably a simple question but I'm curious. What is the purpose

of

the "finally" statement? There must be a good reason to use it that I'm

just

not getting...

How is this:

method1
{
try
{
x;
}
catch
{
y;
}
finally
{
z;
}
}

different than:

method1
{
try
{
x;
}
catch
{
y;
}

z;
}

Thank you,
Joe

[Joe Thompson]

Hi Marina,

That actually makes some sense to me. I guess if no returns were coded in
the try or catch blocks then the second way I showed would work the same as
the first then?

Thanks again,
Joe

"Marina" wrote:

Often, there will be return statements either in the Try or the Catch, or
both. Putting this code in the finally guarantees that it will be executed
in any case. Where as otherwise, you would have to put a copy of it in the
Try and Catch right before the return.

"Joe Thompson" <Jo*********@di scussions.micro soft.com> wrote in message
news:6D******** *************** ***********@mic rosoft.com...

Hi,

This is probably a simple question but I'm curious. What is the purpose
of
the "finally" statement? There must be a good reason to use it that I'm
just
not getting...

How is this:

method1
{
try
{
x;
}
catch
{
y;
}
finally
{
z;
}
}

different than:

method1
{
try
{
x;
}
catch
{
y;
}

z;
}

Thank you,
Joe

[Joe Thompson]

Hi Bruce,

That is a very good example and explanation.

Thanks for the clarification,
Joe

"Bruce Wood" wrote:

The answer is that in your second example, "z" is not guaranteed to be
executed, whereas in your first example, it is.

One caveat, though. Your specific examples were a bit unrealistic: it's
bad style to simply have a "catch" without saying what to catch, a
"catch-all" if you'll pardon the pun. So the way that your examples are
written, the only way that "z" will not be executed in the second
example is if "y" throws an exception (inside the catch block).

A more realistic case would be one in which the "catch" blocks catch
specific exceptions, in which case you need "finaly" in case some other
kind of exception that you're not catching occurs.

Sometimes people (like me) even use "finally" with no "catch" at all:
we want the exceptions to percolate up to the caller, but we have to be
sure to release some resource, reset some value, or change some setting
before leaving.

In my code, changing the cursor to an hourglass is a good example:

// Change the cursor to an hourglass
try
{
.... do a long, slow, complicated operation...
}
finally
{
// Change the cursor back to the default
}

I change the cursor back to a default in the finally block because I
want that to happen _even if_ the complex operation inside the "try"
blows up. In fact, the operation is complex enough that it has already
blown up on me several times for reasons beyond my control. If my
"Change the cursor back" code weren't within the "finally" then my
cursor would be stuck as an hourglass.

[Jeff Louie]

Joe...
try
{
OpenToiletLid() ;
Flush();
}
catch(OverflowE xception e)
{
CallPlumber();
}
finally
{
CloseToiletLid( );
}

Regards,
Jeff

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[Jack Addington]

I think my wife would like that if I could find a way to implement the
finally at home :-)

"Jeff Louie" <je********@yah oo.com> wrote in message
news:O4******** ******@TK2MSFTN GP09.phx.gbl...

Joe...
try
{
OpenToiletLid() ;
Flush();
}
catch(OverflowE xception e)
{
CallPlumber();
}
finally
{
CloseToiletLid( );
}

Regards,
Jeff

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Don't just participate in USENET...get rewarded for it!

[Anders Borum [.NET/C# MCP]]

Hello!

I think my wife would like that if I could find a way to implement the
finally at home :-)

LOL!

Another approach - ask your wife to implement ICareless :-)

--
With regards
Anders Borum / SphereWorks
Microsoft Certified Professional (.NET MCP)