Using C# regular expressions to remove HTML tags

Question

How do I use C# regular expression to replace/remove all HTML tags, including the angle brackets? Can someone please help me with the code?

Answer 1

Regex regex = new Regex(@"</?\w+((\s+\w+(\s*=\s*(?:"".*?""|'.*?'|[^'"">\s]+))?)+\s*|\s*)/?>", RegexOptions.Singleline);

Source

Answer 2

You can use RegEx.Replace() to accomplish this

RegEx objRegExp = new RegEx("<(.|\n)+?>");       
String strOutput = objRegExp.Replace(strHTML, String.Empty)

Answer 3

As often stated before, you should not use regular expressions to process XML or HTML documents. They perform not very well with HTML and XML documents because there is no way to express nested structures in a general way.

You could use the following.

String result = Regex.Replace(htmlDocument, @"<[^>]*>", String.Empty);

This will work for most case, but there will be cases - for example CDATA containing angle brakets - where this will not work as exspected.

Answer 4

The correct answer is don't do that, use the HTML Agility Pack.

Answer 5

Very hard to do 100%. HTML is so flexible that browsers will render fine but a regex would fail. IE doesn't even need end tags. If you know you're going to have clean HTML you should be fine.

Answer 6

The question is too broad to be answered definitively. Are you talking about removing all tags from a real-world HTML document, like a web page? If so, you would have to:

• remove the <!DOCTYPE declaration or <?xml prolog if they exist
• remove all SGML comments
• remove the entire HEAD element
• remove all SCRIPT and STYLE elements
• do Grabthar-knows-what with FORM and TABLE elements
• remove the remaining tags
• remove the <![CDATA[ and ]]> sequences from CDATA sections but leave their contents alone

That's just off the top of my head--I'm sure there's more. Once you've done all that, you'll end up with words, sentences and paragraphs run together in some places, and big chunks of useless whitespace in others.

But, assuming you're working with just a fragment and you can get away with simply removing all tags, here's the regex I would use:

@"(?></?\w+)(?>(?:[^>'""]+|'[^']*'|""[^""]*"")*)>"

Matching single- and double-quoted strings in their own alternatives is sufficient to deal with the problem of angle brackets in attribute values. I don't see any need to explicitly match the attribute names and other stuff inside the tag, like the regex in Ryan's answer does; the first alternative handles all of that.

In case you're wondering about those (?>...) constructs, they're atomic groups. They make the regex a little more efficient, but more importantly, they prevent runaway backtracking, which is something you should always watch out for when you mix alternation and nested quantifiers as I've done. I don't really think that would be a problem here, but I know if I don't mention it, someone else will. ;-)

This regex isn't perfect, of course, but it's probably as good as you'll ever need.

Answer 7

thanks all for your valuable inputs!

Answer 8

(XElement.Parse(xmlString)).Value :)

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