Hmmm, I think it also depends on what you 'expect' the app to be doing
If you think that in most cases the string will be an integer, then there is little overhead using the exception method, only when a non-integer string is passed will the exception be invoked. If however, there is a good chance that the strings being processed may not be integers then it's a bad idea, as the exceptions are expensive in this case.
Also one other thing to consider is what the TryParse function actuall does (I don't know this myself) but it could use exceptions internally, and just return false if it catches one
There's my 2 pence worth :)
Matt
Message
From: CSharpNET (AT) yahoogroups (DOT) com [mailto:CSharpNET (AT) yahoogroups (DOT) com] Behalf Paul Cowan
Sent: 16 November 2005 13:42
To: CSharpNET (AT) yahoogroups (DOT) com
Subject: Re: [C#.NET] RE: TryParse vs. Exception
The general consensus says you should never test a condition with an exception.
I do say that somewhat hypocritically. I recently wanted to test a date's validity and the best I came up with was the following:
try
{
string[] dateParts = DateTime.Parse(etaString, Root.UiCultureInfo,).ToString("HH:mm
UTC, dd-MM-yy").Split(',');
}
catch
{
RenderTd(_etaTd, status, etaString); }
Where I am indeed doing the complete opposite. Has anyone a nice solution to this.
Paul
dagda1 (AT) hotmail (DOT) com

>From: David Lanouette <David.Lanouette (AT) gmail (DOT) com>
>Reply-To: CSharpNET (AT) yahoogroups (DOT) com
>To: CSharpNET (AT) yahoogroups (DOT) com
>Subject: Re: [C#.NET] RE: TryParse vs. Exception
>Date: Wed, 16 Nov 2005 08:33:40 -0500
>
>I don't have a specific answer, but I know that Exceptions are
>generally expensive. I would /guess/ that the TryParse method would be
>the better preformer.
>
>
11/16/05, Peter H <peter.hartlen (AT) sib (DOT) sewrote:
Hi!
Is there a known difference in performance between checking if a
string
>is
Numeric (integer in this case) using Double.TryParse() or catching
an exception?
i.e.
try
{
return Convert.ToInt32("234a234"); } catch( FormatException ) {
return Int.MinValue;
}
vs.
double dTmpNum;
if( Double.TryParse( Double.TryParse(sNumber, NumberStyles.Integer,
NumberFormatInfo.CurrentInfo, out dTmpNum)) ) {
return Convert.ToInt32(dTmpNum); } else {
return Int.MinValue;
}
Thanks,
Peter
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If you're familiar with VB6, it's similar to the IsNumeric function. It
checks if a value is numeric before it attempts the cast, but has the
additional functionality of returning the double (final parameter) if the
cast is valid.

I found this article by googling Double.TryParse benchmark.
http://aspalliance.com/80

It seems that it is little more than wrapped Try{}Catch{} block, as the
performance was nearly the same. My guess is it's a helper function that
will allow more concise code.

What's interesting to me is the incremental char method.

11/16/05, Peter B <peter.hartlen (AT) sib (DOT) sewrote:

In CSharpNET (AT) yahoogroups (DOT) com, "Matt Evans" < matt@twrote:
Also one other thing to consider is what the TryParse function
actuall does (I don't know this myself) but it could use exceptions
internally, and just return false if it catches one

Exactly!

That's why I am hoping someone knows this for a fact.

/ Peter
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yeah sorry - I didn't edit my email before I sent. With a NUMBER it's
nearly the same with a non-number, TryParse is faster.

apologies.

11/16/05, Peter H <peter.hartlen (AT) sib (DOT) sewrote:

Hello Sam!

Not really, I also read the article and it says exactly the opposit. The
performance hit of try-catch is a lot greater than what you get using
Double.TryParse. I'm eager to agree with Brett's statment that
Double.TryParse is definitely created to prevent the exception overhead
when
checking numbers.

the other hand, Visual Basic's IsNumeric function is a simple wrapper
using try-catch itself. This is what I have read and the tests I did
confirms the theory.

Also, John, that link you provided to Int32.TryParse, is for WinFX SDK.
(which I don't really know what it is).
Int32.TryParse is not part of the standard .NET Framework v. 1.1 is it?

__ So how about getting that string to an Integer (not double) __
I used the code inte the article <http://aspalliance.com/80>
http://aspalliance.com/80 and also created a function (that uses
Double.TryParse) to validate the string as an integer AND convert the
resulting double into an integer. The performance hit of the conversion
was
very small, and compared to using try-catch it's a lot faster!

BUT! To my horror I discovered that the use of

double.TryParse(strInputVal,
NumberStyles.Integer,
NumberFormatInfo.CurrentInfo,
out dVal);

Does not return false if the value is above Int32.MaxValue, it seems like
it
simply makes sure strInputVal consists of numbers only (not how many)
could this be true?

/ Peter
--
Message
From: CSharpNET (AT) yahoogroups (DOT) com [mailto:CSharpNET (AT) yahoogroups (DOT) com]
Behalf
Sam Acheson
Sent: Wednesday, November 16, 2005 5:02 PM
To: CSharpNET (AT) yahoogroups (DOT) com
Subject: Re: [C#.NET] RE: TryParse vs. Exception
--
If you're familiar with VB6, it's similar to the IsNumeric function. It
checks if a value is numeric before it attempts the cast, but has the
additional functionality of returning the double (final parameter) if the
cast is valid.

I found this article by googling Double.TryParse benchmark.
http://aspalliance.com/80

It seems that it is little more than wrapped Try{}Catch{} block, as the
performance was nearly the same. My guess is it's a helper function that
will allow more concise code.

What's interesting to me is the incremental char method.

11/16/05, Peter B <peter.hartlen (AT) sib (DOT) sewrote:

In CSharpNET (AT) yahoogroups (DOT) com, "Matt Evans" < matt@twrote:
Also one other thing to consider is what the TryParse function
actuall does (I don't know this myself) but it could use exceptions
internally, and just return false if it catches one

Exactly!

That's why I am hoping someone knows this for a fact.

/ Peter
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WinFX is new. It's the combination of Avalon and Indigo but I'm not sure if
it is still in beta or if it has been released as part of .NET 2.0. Either
way, I think you're right about it not being a part of the 1.1 framework.

I like the article that Brett dug up.

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>Does not return false if the value is above Int32.MaxValue, it seems like it
>simply makes sure strInputVal consists of numbers only (not how many)
>could this be true?

Remember, this function is checking for Doubles, not Ints. The
NumberStyle just tells what type of double is allowed. So, looks like
you have an extra step after converting to a double - check if it is
between Int32.MinValue and Int32.MaxValue.

- David Lanouette
- David.Lanouette (AT) GMail (DOT) com

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My current understanding is that Avalon / Indigo will not be in
production release until the Vista release time frame, about a year from
now. At that point it will bolt onto Windows XP/2003 as well.

It's probably in some kind of beta and while I'm not sure I care that
much about Avalon for line of business apps, any project needing
interprocess communications and with a release time frame of 2007 or
later should probably be architecting for Indigo at this point, since
it's a completely different API from Remoting.

John Johnson II wrote:

>WinFX is new. It's the combination of Avalon and Indigo but I'm not sure if
>it is still in beta or if it has been released as part of .NET 2.0. Either
>way, I think you're right about it not being a part of the 1.1 framework.
>
>I like the article that Brett dug up.
>

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