Regex Pattern for Whitespace

Question

I am creating a regex library to work with HTML (I'll post it on MSDN Code when it's done). One of the methods removes any whitespace before a closing tag.

<p>See the dog run </p>

It would eliminate the space before the closing paragraph. I am using this:

    public static string RemoveWhiteSpaceBeforeClosingTag(string text)
    {
        string pattern = @"(\s+)(?:</)";
        return Regex.Replace(text, pattern, "</", Singleline | IgnoreCase);
    }

As you can see I am replacing the spaces with </ since I cannot seem to match just the space and exclude the closing tag. I know there's a way - I just haven't figured it out.

FYI, both the Singleline and IgnoreCase modifiers are irrelevant, as there are no dots or letters in the regex. — Alan Moore
– Alan Moore, Commented May 22, 2009 at 22:19

cletus · Accepted Answer · 2009-05-30 09:21:30Z

11

\s+(?=</)

is that expression you're after. It means one or more white-space characters followed by

(?=...) is a positive lookahead. This won't be included in the expression;
(?:...) is a non-capturing group. This will be included in the expression.

That all being said, regular expressions are a flaky and error-prone way of processing HTML so should be used with caution if at all.

edited May 30, 2009 at 9:21

answered May 22, 2009 at 15:38

cletus

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1 Comment

Tony Basallo Over a year ago

That was it - thanks. I wish there was an alternative to processing the HTML I'm getting. You should have seen the IndexOf and LastIndexOf code that this is replacing 8-\

Daniel Martin · Accepted Answer · 2009-05-22 15:38:49Z

3

You want a lookahead (?=) pattern:

\s+(?=</)

That can be replaced with ""

answered May 22, 2009 at 15:38

Daniel Martin

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