Regex gives compiler error

Question

<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:"[^"]*"|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>

Above is the regex which I took from Remove all empty HTML tags? and I am trying to use the same below :-

string regex= @"<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:"[^"]*"|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>";

And I get many compile errors like - newline in constant, unrecognized escape sequence on the above line itself.

Could anybody help me by pointing what am I missing?

Answer 1

You have double quotes inside the regexp that need to be quoted.

 string regex= @"<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:"[^"]*"|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>";

should be

string regex= @"<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:\u0022[^\u0022]*\u0022|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>";

Btw, because of the <\/\1\s*> this will only remove balanced tags surrounding space. It will match <p> </p> but not <img src=bogus onerror=alert(1337)>.

Even if all you want to do is remove balanced tags around space, be aware that this will not match all such tags. Specifically, it will not match tags where the tag name varies by case: <p> </P>.

Finally, it will not remove transitively empty tags: <i><b></b></i> -> <i></i>.

Answer 2

You need to use "" for double quotes inside the string:

string regex= @"<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:""[^""]*""|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>";

Answer 3

Single double quotes( " ) have to be escaped with double double quotes ( "" ) in verbatim strings.

Try this

string regex= @"<(\w+)\b(?:\s+[\w\-.:]+(?:\s*=\s*(?:""[^""]*""|'[^']*'|[\w\-.:]+))?)*\s*/?>\s*</\1\s*>";