Benchmarking IsNumeric Options
page 1 of 4
Published: 14 Oct 2003
Unedited - Community Contributed
Which IsNumeric method should you use? Check this article out to find out!
by J. Ambrose Little
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Views (Total / Last 10 Days): 51824/ 71


Originally Published: 11 July 2003

One of the frequently asked questions in various .NET developer venues is "how can I check for a numeric value if I am using C#?" The question itself is not precise because it applies equally to other .NET languages, but those using VB.NET, particularly those with a VB or VBScript background, take the IsNumeric function for granted.  What they and many new .NET developers don't know is that this function is actually contained in Microsoft's Microsoft.VisualBasic.dll assembly, which can be used by any .NET language.  So the comparisons in this article are just as valid for VB.NET programmers as they are for those programming in other languages.


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User Comments

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Title: Straight to the point   
Name: Fabio C. Rispoli
Date: 2006-08-01 4:16:33 PM
Congratulations for the article. Simple and straight to the point.

Title: Mr.   
Name: mike
Date: 2006-04-05 10:30:42 AM
double.TryParse is also slower than Incremental Chars.
Title: Gopal   
Name: Ambrose
Date: 2006-03-22 1:19:05 PM

It's been a long time that I looked at this, but I seem to recall that the VB code didn't use double.TryParse. Maybe it was updated? Are you looking at v2 because this was written before v2 was in alpha...
Title: Another note   
Name: gopal
Date: 2006-03-22 1:13:08 PM
Incremental char returns true for empty strings.
Also, looking at the disassembly code, Visualbasic Isnumeric uses Double.TryParse.
Title: just a note   
Name: E
Date: 2006-02-16 3:37:19 PM
I was just noticing that the Incremental Char method returns false for negative numbers. . .
Title: IsNumeric?   
Name: Peter Hartlén
Date: 2005-11-17 3:31:17 AM
First of all, I did the test with converting a string to integer. Although the code needed for this was a bit more than I at first expected, the performance overhead (compared to simple TryParse) was not that much. The code I used:

public bool TryParseToInt ( string expression, out int iIntVal )
double dVal;
bool bRes;

bRes = double.TryParse(expression,
out dVal);

if( dVal > Int32.MaxValue || dVal < Int32.MinValue )
iIntVal = 0;
bRes = false;
iIntVal = Convert.ToInt32(dVal);

return bRes;

As you can see, this method both tests if the string is a valid integer (Int32), and if so, converts the value using the out parameter.

Regarding your results (compared to mine):

Are you sure the data for VB's IsNumeric is correct? During my tests it shows the same performance as try-catch blocks. I’ve read that IsNumeric uses try/catch itself, so it’s merely a wrapper.

The execution time for the Regular Expression method increases quite dramatically when I increase the length of the input string and the faulty character is at the end.

Also worth mention, I did a test with 1 million strings where 2% where faulty (i.e. non-numbers). The performance between a try-catch block function and a TryParse-based function was negligible. So in the real life (where you won’t find 100% correct nor 100% erroneous data), the result looks quite different!
Title: Have to be careful   
Name: Steve Maier
Date: 2005-11-16 11:38:30 AM
One thing to remember tho with the incremental character approach is localization. some places use ',' for the decimal point and '.' for the grouping character. With the Parse and TryParse methods, they can take the culture value and will parse things correctly.
Title: Nice reading!   
Name: Peter Hartlén
Date: 2005-11-16 10:16:27 AM
Thanks, this was exactly what I was looking for!

I'm using Compact Framework and for example Int32.TryParse is not available, it would be interesting to see the performance of Double.TryParse (using NumberFormat.Integer), with a cast to Int32. I will try this using your code!

Thanks again!
Title: Thanks for the article !   
Name: Deon
Date: 2005-11-02 8:43:18 AM
Great article.

Thanks for the effort
Title: Ms.   
Name: Ututu
Date: 2005-08-09 12:32:04 PM
Very good article, thanks a lot.
Title: Try-Catch   
Name: J. Ambrose Little
Date: 2005-07-20 8:13:44 AM
Try-catch statements are integral to a good program, but they should only be used where they need to be used. There are some good topics on Exception Management in the MSDN Library that you should review to better understand.
Title: Mr.   
Name: Ram Kinkar Pandey
Date: 2005-07-20 5:24:46 AM
I was just Looking why using try..catch in ASP.NET is bad idea. This article makes this very clear to me.
Thank you
Title: Mr.   
Name: Linanga Keeba
Date: 2005-07-18 2:23:36 PM
The article assisted me very much. Thanks.

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