C# | Regex Dotall and Result Match

Question

To the point, how i can enable dotall flags on C# Regex ? And i have this regex.

string reg = "<table>.*</table>";

And for example, i regexed this html text

<table id="table1">
<table id="table2">
</table>
</table>

Where does my regex stop the match ? The first </table> or the second </table>

Thanks guys.. :)

A more interesting example is `
` - Your regex will match from the first `""` to the last `"
"` (so it will **match nothing** in case of your input - you have attributes). Also, if you have two questions, please post two questions `:)` — Kobi, Jun 09 '11 at 09:14
@leppie, i'd rather use REGEX rather than Xpath on HTML/XML. Can you give me other resources to search strings or anything in HTML Files accurately ? — Aditya Avaga Purwa, Jun 09 '11 at 09:36
@Aditya Avaga Purwa: Thats like saying you want to use diesel in your petrol car cause diesel smells better. It aint gonna work, buddy! — leppie, Jun 09 '11 at 09:39

score 3 · Answer 1 · answered Jun 09 '11 at 09:10

3

Regular expressions are greedy by default, gobbling up as much as possible. Therefore, it'll stop at the second table.

You can change this by applying the question mark modifier.

<table>.*?</table>

That said, you'll need to make sure that your regex is set up to cover multiple lines of text.

answered Jun 09 '11 at 09:10

Paul Alan Taylor

10,474
1
26
42

What about if i have this `
` ? Will its stop at the last or the second ? Or the first ? – Aditya Avaga Purwa Jun 09 '11 at 09:12
When using `.*?` it will match `
`, so the first `` it finds will end the match. DON'T use regex for this, you want to a proper parser... – Qtax Jun 09 '11 at 09:28
Have to agree with Qtax. Regex is not the correct solution for parsing markup. You've demonstrated this with your own example. – Paul Alan Taylor Jun 09 '11 at 09:34
@Qtax: what i want is ,Regex stop at the /table where its started. – Aditya Avaga Purwa Jun 09 '11 at 09:38
1

What exactly are you trying to do? – Paul Alan Taylor Jun 09 '11 at 09:51
@Paul Alan Taylor : I want to create HtmlParser Class to get the attributes, element, or anything related to html. – Aditya Avaga Purwa Jun 09 '11 at 09:56
@Purwa, that's a different question, see http://stackoverflow.com/questions/100358/looking-for-c-html-parser – Qtax Jun 09 '11 at 10:26

score 2 · Answer 2 · answered Jun 09 '11 at 09:11

2

* is a 'greedy' operator - i.e. it eats up as much as possible, so it will match between the first <table> and the second </table> (providing the regular expression is configured to match over multiple lines). You can cause it to be 'non-greedy' by using *? instead.

answered Jun 09 '11 at 09:11

mdm

12,480
5
34
53

What about if i have this `
` ? Will its stop at the third or the second ? Or the first ? – Aditya Avaga Purwa Jun 09 '11 at 09:17

score 0 · Answer 3 · answered Nov 02 '17 at 12:43

Dotall is a regexflag so you can use like: Regex.Replace(input, regex, replace, RegexOptions.Singleline | RegexOptions.IgnoreCase)

Dotall = RegexOptions.Singleline , since it treat the string as a single line.

you can also modify regex flag in the middle of the regex instruction, like in: (?s) - Match the remainder of the pattern with the following effective flags: migs (Multiline, ignorecase, global, and singleline)

C# | Regex Dotall and Result Match

3 Answers3