try/catch/finally

[Alexander Mueller]

I have always wondered what finally is actually for. What would be the
exact difference between

try
{
somecode1();
}
catch(Exception )
{
somecode2();
}
finally
{
somecode3();
}

somecode4();
..... and ....
try
{
somecode1();
}
catch(Exception )
{
somecode2();
}

somecode3();
somecode4();
Thanks,
Alexander

[Cor Ligthert]

Alexander,

Even when you set a return somewhere, the finally will be executed.

Cor

[Olaf Baeyens]

> I have always wondered what finally is actually for. What would be the

exact difference between

The finally gets ALWAYS executed, even when an exception is thrown.
And it doesn't block the thrown exception, it just executes the finally part
and continues with the exception.

A very good example for this would be to close a file in there.
This way the file is always closed even if an exception occurs.

--
http://www.skyscan.be

[Remigiusz Dybka]

The difference is that the finally-block will be executed no matter what
happens (uncaught exceptions, exceptions thrown in catch-block and so
on). If your application fails, the first example will execute
somecode3() but not somecode4() as it will never get to that point. The
second example won't execute any of them (if the app fails, of course).
Finally is ideal for things like releasing database-connections, closing
files, sockets and other clean-up operations.

I have always wondered what finally is actually for. What would be the
exact difference between

try
{
somecode1();
}
catch(Exception )
{
somecode2();
}
finally
{
somecode3();
}

somecode4();
.... and ....
try
{
somecode1();
}
catch(Exception )
{
somecode2();
}

somecode3();
somecode4();
Thanks,
Alexander

[Richard Blewett [DevelopMentor]]

Also, you are much more likely to want to perform some kind of cleanup rather than actually deal with an exception (theres no point in downstream code unless it can do something about the error). So you will much more commonly see the following than try ... catch.

// allocate some resource
try
{
// use the resource
}
finally
{
// clean up the resource
}

The clean up will occur whether ot not an exception occurs in the try block

Regards

Richard Blewett - DevelopMentor
http://www.dotnetconsult.co.uk/weblog
http://www.dotnetconsult.co.uk

Alexander,

Even when you set a return somewhere, the finally will be executed.

Cor

[Alexander Mueller]

Cor Ligthert wrote:

Alexander,

Even when you set a return somewhere, the finally will be executed.

Cor

Thanks Cor, but where "somewhere" exactly?

Alexander

[Alexander Mueller]

Olaf Baeyens wrote:

The finally gets ALWAYS executed, even when an exception is thrown.
And it doesn't block the thrown exception, it just executes the finally part
and continues with the exception.

A very good example for this would be to close a file in there.
This way the file is always closed even if an exception occurs.

Thanks Olaf, so its the conclusion in my reply to Richard's posting?

Alexander

[Alexander Mueller]

Richard Blewett [DevelopMentor] wrote:

Also, you are much more likely to want to perform some kind of cleanup rather than actually deal with an exception (theres no point in downstream code unless it can do something about the error). So you will much more commonly see the following than try ... catch.

// allocate some resource
try
{
// use the resource
}
finally
{
// clean up the resource
}

The clean up will occur whether ot not an exception occurs in the try block

So the actual difference is, that try/catch/finally doesnt make much
sense and by having try/finally the exception will be actually thrown as
normally to the caller (as if unhandled) but prior the code in finally
will be executed, right?

Alexander

[Alexander Mueller]

Remigiusz Dybka wrote:

The difference is that the finally-block will be executed no matter what
happens (uncaught exceptions, exceptions thrown in catch-block and so
on). If your application fails, the first example will execute
somecode3() but not somecode4() as it will never get to that point. The
second example won't execute any of them (if the app fails, of course).
Finally is ideal for things like releasing database-connections, closing
files, sockets and other clean-up operations.

Thanks Remigiusz, but I dont see a reason why those should not be
executed. After all the exception is caught by the catch statement.

Alexander

[Hans Kesting]

Alexander Mueller wrote:

Cor Ligthert wrote:

Alexander,

Even when you set a return somewhere, the finally will be executed.

Cor

Thanks Cor, but where "somewhere" exactly?

Alexander

in the "try" or "catch" block

--
Hans Kesting