Question

I am converting some code from Perl into .NET. I have this s/// pattern replacement:

$text =~ s/<A HREF="([^"]+)">\Q\1\E</A>"/$1/gi;

I use the Perl \Q and \E to escape the text I am matching in the first capture, the URL portion of an HREF attribute.

How do I do the same thing in .NET? I’ve read about using Regex.Escape() to escape text for a regular expression, but how can I use it WITHIN the regular expression that is performing the match? (Or do I even need to do that?)

So right now I’m not doing anything special, and wondering if this will continue to work as well as my Perl regex has been:

text = Regex.Replace(text, @"<A HREF=""([^""]+)"">\1</A>", "$1", RegexOptions.IgnoreCase);

Answer 1

You don’t need the \Q…\E in the Perl. In fact, it will keep your Perl from working, because it means the ‘\1’ is taken literally instead of being replaced with the contents of the first match.

\Q…\E is for quoting characters that are special in a regex. The string replaced with a backreference is already taken literally, not re-evaluated as regular expression syntax.

The same goes for anything inserted into the replacement string. You only need \Q…\E, or Regex.Escape(), if you have a variable from outside of regex-land with text that you want to interpolate into a regular expression, without accidentally treating parts of it as a regular expression metacharacters.