Re: uncaught exception handlers - C# Discussion Boards

MidwestLimey29-Apr-08 11:43

29-Apr-08 11:43

Spacix One wrote:
The problem is when Exceptions do occur it slows everything down. Though I think that is better than the WHOLE app crashing to a grinding halt and a .NET error message dialog showing then the Microsoft error reporting tool (if enabled) poping up.

You mean you don't think users like that? Big Grin | :-D

I'm largely language agnostic  
     After a while they all bug me  

Re: uncaught exception handlers

George_George29-Apr-08 19:58

George_George

29-Apr-08 19:58

Thanks Spacix,

What do you mean "using exceptions to contol logic"? We should never throw any exception when there is some logical errors during runtime?

regards,
George

Re: uncaught exception handlers

Spacix One2-May-08 5:18

Spacix One

2-May-08 5:18

Like in my second code block, if you throw in your method and you catch it to only return something less complex, or change your structure.

Hmm better example:

(This is an intentional BAD code example!)

static FileStream openFile(string filePath)
{
    FileStream fs;
    try
    {
        fs = File.OpenRead(filePath);
    }
    catch (FileNotFoundException err)
    {
        File.Create(filePath);
        fs = File.OpenRead(filePath);
    }
    return fs;
}

That is bad because you could just used
File.Exist() to check for the file before opening it, and make it before trying to call OpenRead() on it. I know this is pointless but still an example of a NEVER do...

-Spacix
All your skynet questions[^] belong to solved

I dislike the black-and-white voting system on questions/answers. Dead | X|

Re: uncaught exception handlers

George_George2-May-08 21:29

George_George

2-May-08 21:29

Thanks for your clarification, Spacix!

regards,
George

Re: uncaught exception handlers

MidwestLimey29-Apr-08 11:42

MidwestLimey

29-Apr-08 11:42

I mean the code within the block doesn't magically slow down, however establishing the try catch block and then tearing it down does use some cycles.

I'm largely language agnostic  
     After a while they all bug me  

Re: uncaught exception handlers

George_George29-Apr-08 19:59

George_George

29-Apr-08 19:59

Thanks for clarifying this, MidwestLimey!

regards,
George

Re: uncaught exception handlers

Derek Bartram30-Apr-08 5:23

Derek Bartram

30-Apr-08 5:23

MidwestLimey wrote:
I once worked on a project where the Project Lead insisted on try catch blocks in every bloody method.

That sounds a little overkill, however generally I do use try...catch blocks in all my gui event handlers so that application is a little more useful when something does go wrong.

MidwestLimey wrote:
I did some performance testing and could determine definitive costs with the setup and teardown of the block, but was unable to measure any discernable difference to the code internally.

However the code was entirely managed, perhaps wrapping unmanaged code has other implications.

Thank you for that, personally that is of great interest. I'm actually in the middle of writing a series of articles on language performance so hopefully i'll be able to give further insite on this.

Many thanks,
Derek Bartram

Re: uncaught exception handlers

George_George26-Apr-08 21:23

George_George

26-Apr-08 21:23

Thanks Spacix,

I think when you get exception, and uncaught it, your program will terminate and you will get information from console, for example. In this way, you can know what exception happens.

So, no need to catch all exceptions, right?

regards,
George

Re: uncaught exception handlers

George_George26-Apr-08 21:14

George_George

26-Apr-08 21:14

Thanks Derek,

1.

Derek Bartram wrote:
to avoid using try...catch as much as possible due to the massive performance hit it

Do you mean catching all exception will degrade performance or you mean generally exception handling approach will degrade performance?

2.

Do you have any documents to support your points? Smile | :)

regards,
George

Re: uncaught exception handlers

Derek Bartram27-Apr-08 0:12

Derek Bartram

27-Apr-08 0:12

I've just done some googling on the subject (and confirmed via a lecturer from Uni)....

1) There is a performance hit running code inside a try...catch block but it's negligable
2) There is a BIG performance hit when an exception occurs

So,

3) Use try...catch for only catching untestable errors and not controlling programming flow.

http://www.javaworld.com/javaworld/javaqa/2001-07/04-qa-0727-try.html[^]

http://aspadvice.com/blogs/name/archive/2008/01/18/Try-Catch-Performance-in-CSharp_3A00_-A-Simple-Test-Response.aspx[^]

Re: uncaught exception handlers

George_George27-Apr-08 2:08

George_George

27-Apr-08 2:08

Thanks Derek,

Cool!!

Your 1st link is Java... Smile | :)

I am interested in your 2nd link. But confused what means "catching untestable errors" and
"not controlling programming flow"? Could you show some samples please?

regards,
George

Re: uncaught exception handlers

Derek Bartram30-Apr-08 1:49

Derek Bartram

30-Apr-08 1:49

George_George wrote:
But confused what means "catching untestable errors"

//writer is a stream writer to a file..
try
{
writer.Write("Hello");
}
catch (Exception err)
{
//handle error
}

In this case you couldn't test for every possible error as some are far out the scope of plausible; e.g. can't access the file as it was on a removable drive that was just unplugged.

George_George wrote:
"not controlling programming flow"?

//slider is a silder whos value is 0 to 100
double y = 100.0 / slider.Value

then

try
{
double y = 100.0 / slider.Value
}
catch (Exception)
{
//handler exception
}

is a bad way to write this code (remembing slider.Value could be 0 causing divide by 0 exception), a better way would be....

if (slider.Value != 0)
{
double y = 100.0 / slider.Value
}
else
{
handle error
}

Re: uncaught exception handlers

George_George30-Apr-08 3:58

George_George

30-Apr-08 3:58

Thanks Derek,

I agree with your sample one. But for the sample two, I can not see any advantage for the 1st sample. Because for the 2nd you preferred sample, when we write code for "handle error" in else bracket, we usually throw exception. So, both samples have the same effect of exception thrown when we met with divide by zero issues.

So, what do you think are the advantages?

try
{
double y = 100.0 / slider.Value
}
catch (Exception)
{
//handler exception
}

is a bad way to write this code (remembing slider.Value could be 0 causing divide by 0 exception), a better way would be....

if (slider.Value != 0)
{
double y = 100.0 / slider.Value
}
else
{
handle error
}

regards,
George

Re: uncaught exception handlers

Derek Bartram30-Apr-08 4:54

Derek Bartram

30-Apr-08 4:54

The point is sample two doesn't throw an exception but rather just run a different section of code. An if statement inherinatly has less overhead than that of a try...catch statement. Certainly both will perform exactly the same function however the second will run more efficiently and quicker.

Re: uncaught exception handlers

George_George30-Apr-08 5:08

George_George

30-Apr-08 5:08

Thanks for your clarification, Derek!

It is clear now. Smile | :)

regards,
George

Re: uncaught exception handlers

PIEBALDconsult27-Apr-08 4:37

PIEBALDconsult

27-Apr-08 4:37

Derek Bartram wrote:
massive performance hit

Perhaps you haven't read this[^] yet.

Re: uncaught exception handlers

Derek Bartram27-Apr-08 6:56

Derek Bartram

27-Apr-08 6:56

Thanks for the link, an interesting article. I probably didn't specify 'massive' which didn't help; I meant relative to performing an if test to prevent the exception.

Re: uncaught exception handlers

George_George27-Apr-08 20:17

George_George

27-Apr-08 20:17

Thanks Derek,

What do you mean "didn't specify 'massive' which didn't help" and "relative to performing an if test to prevent the exception"? Could you show more description or some pseudo code about your approach please?

regards,
George

Re: uncaught exception handlers

Derek Bartram30-Apr-08 5:08

Derek Bartram

30-Apr-08 5:08

Firstly, from above

//writer is a stream writer to a file..
try
{
writer.Write("Hello");
}
catch (Exception err)
{
//handle error
}

In this case you couldn't test for every possible error as some are far out the scope of plausible; e.g. can't access the file as it was on a removable drive that was just unplugged.

George_George wrote:
"not controlling programming flow"?

//slider is a silder whos value is 0 to 100
double y = 100.0 / slider.Value

then

try
{
double y = 100.0 / slider.Value
}
catch (Exception)
{
//handler exception
}

is a bad way to write this code (remembing slider.Value could be 0 causing divide by 0 exception), a better way would be....

if (slider.Value != 0)
{
double y = 100.0 / slider.Value
}
else
{
handle error
}

George_George wrote:
What do you mean "didn't specify 'massive' which didn't help"

It's all very well saying massive improvement or whatever, but if you don't give some quantative value or referance, massive has no meaning (it could save 0.1ms which in terms of clock cycle is alot, but probably less significant to compared to a complex if statement).

Re: uncaught exception handlers

George_George30-Apr-08 5:11

George_George

30-Apr-08 5:11