The simple regex expression [0-9]* does not work with {e|24} in C#

Question

I've been working on my own simple Wikipedia parser in C#. So far I'm not getting very far because of this problem.

I extract the string {e|24} but it could contain any number. All I want to do is simply extract the number from this string.

This is the code I am using currently:

Match num = Regex.Match(exp.Value, "[0-9]*");
Console.WriteLine(num.Value);

However num.Value is blank.

Can someone please explain why this is not working and how I can fix it?

This is trivial to test in a tool. I use http://www.radsoftware.com.au/regexdesigner/ which will give you exact results for .NET. — Chuck D, Jan 09 '13 at 23:56
To further explain why this didn't work, [0-9]* actually matches your string in 6 places: `><{e|24}`, `{><|24}`, `{e|>24<}`, `{e|24><}`, and `{e|24}><`. So it did find the part you wanted, but it also matched 5 empty strings, and Match() only returns the first match. — JLRishe, Jan 10 '13 at 00:51

score 6 · Accepted Answer · answered Jan 09 '13 at 23:53

6

You would want to use [0-9]+ to ensure at least one number. [0-9]* allows it to be matched 0 times or more, thus getting blanks

answered Jan 09 '13 at 23:53

CorrugatedAir

score 1 · Answer 2 · answered Jan 09 '13 at 23:59

1

My suggestion, make the regexp: \d+

Works. Simpler. Shorter, uses no groups or ranges.

answered Jan 09 '13 at 23:59

hjc1710

1

[0-9] and \d are not the same identifier in .Net, see: http://stackoverflow.com/questions/273141/regex-for-numbers-only – Preston Guillot Jan 10 '13 at 00:26
Ok, but unless the string is going to contain numerals from other languages (and OP doesn't want to match them), \d should do fine. – JLRishe Jan 10 '13 at 00:45
Woah, I did not know that. Thanks for sharing. The more you know. – hjc1710 Jan 10 '13 at 02:07

2 Answers2