Regular expression to remove
from

Question

I am trying to remove the <br /> tags that appear in between the <pre></pre> tags. My string looks like

string str = "Test<br/><pre><br/>Test<br/></pre><br/>Test<br/>---<br/>Test<br/><pre><br/>Test<br/></pre><br/>Test"

string temp = "`##`";
while (Regex.IsMatch(result, @"\<pre\>(.*?)\<br\>(.*?)\</pre\>", RegexOptions.IgnoreCase))
{
    result = System.Text.RegularExpressions.Regex.Replace(result, @"\<pre\>(.*?)\<br\>(.*?)\</pre\>", "<pre>$1" + temp + "$2</pre>", RegexOptions.IgnoreCase);
}
str = str.Replace(temp, System.Environment.NewLine);

But this replaces all <br> tags between first and the last <pre> in the whole text. Thus my final outcome is:

str = "Test<br/><pre>\r\nTest\r\n</pre>\r\nTest\r\n---\r\nTest\r\n<pre>\r\nTest\r\n</pre><br/>Test"

I expect my outcome to be

str = "Test<br/><pre>\r\nTest\r\n</pre><br/>Test<br/>---<br/>Test<br/><pre>\r\nTest\r\n</pre><br/>Test"

Is the format of the string always the same, that is, is it regular? Or are you trying to get this out of whole HTML pages that might be in completely different structures? — Oded, Aug 13 '10 at 06:53
*sigh* http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454 — Robin Day, Aug 13 '10 at 06:55
There's a lot of wisdom that regex and html are **not** good friends. It might work for some *limited* scenarios, but personally I'd be using a parser/DOM/whatever here. — Marc Gravell, Aug 13 '10 at 06:55
ok, so if I agree that parsing html with regex is not a good option. so then is it that the regex will only parse tags between first and last `
` tags? — Ashish, Aug 13 '10 at 07:09

score 3 · Answer 1 · edited May 23 '17 at 12:13

3

If you are parsing whole HTML pages, RegEx is not a good choice - see here for a good demonstration of why.

Use an HTML parser such as the HTML Agility Pack for this kind of work. It also works with fragments like the one you posted.

edited May 23 '17 at 12:13

Community

1
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answered Aug 13 '10 at 06:56

Oded

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I am just trying to parse the above string that i mentioned in str. – Ashish Aug 13 '10 at 07:00
That is not answer for the question. That guy asked for regex and nothing more. – DixonD Aug 13 '10 at 07:01

score 2 · Answer 2 · answered Aug 13 '10 at 06:54

2

Don't use regex to do it.

"Be lazy, use CPAN and use HTML::Sanitizer." -Jeff Atwood, Parsing Html The Cthulhu Way

answered Aug 13 '10 at 06:54

user375049

277
6
16

score 0 · Answer 3 · answered Aug 13 '10 at 08:00

        string input = "Test<br/><pre><br/>Test<br/></pre><br/>Test<br/>---<br/>Test<br/><pre><br/>Test<br/></pre><br/>Test";
        string pattern = @"<pre>(.*)<br/>(([^<][^/][^p][^r][^e][^>])*)</pre>";
        while (Regex.IsMatch(input, pattern))
        {
            input = Regex.Replace(input, pattern, "<pre>$1\r\n$2</pre>");
        }

this will probably work, but you should use html agility pack, this will not match <br> or <br /> etc.

score 0 · Accepted Answer · answered Aug 13 '10 at 10:38

Ok. So I discovered the issue with my code. The problem was that, Regex.IsMatch was considering just the first occurrence of <pre> and the last occurrence of </pre>. I wanted to consider individual sets of <pre> for replacements. So I modified my code as

foreach (Match regExp in Regex.Matches(str, @"\<pre\>(.*?)\<br\>(.*?)\</pre\>", RegexOptions.IgnoreCase)) 
{
    matchFound = true;
    str = str.Replace(regExp.Value, regExp.Value.Replace("<br>", temp));
}

and it worked well. Anyways thanks all for your replies.

Regular expression to remove from

4 Answers4

Regular expression to remove
from