Replace an existing url in given text with a new url using Regex

Question

I'm trying to replace an existing url in given text with a new url using regex. I don't seem to get any matches for the regex pattern I'm using:

string regex = "<a href=\"http://domain/page.asp?id=(\\d+)&amp;oid=(\\d+)&amp;type=(\\w+)\">";

Can someone please assist me write a correct pattern to find urls that look like:

"<A href=\"http://domain/page.asp?id=38957&amp;oid=2497&amp;type=JPG\">"

Below is my test code which cannot find any matches for the pattern I'm using:

string result = string.Empty;

string sampleText = "<A href=\"http://domain/page.asp?id=38957&amp;oid=2497&amp;type=JPG\"><U>Click here for Terms &amp; Conditions...</U></A>";

string regex = "<a href=\"http://domain/page.asp?id=(\\d+)&amp;oid=(\\d+)&amp;type=(\\w+)\">";
        Regex regEx = new Regex(regex, RegexOptions.IgnoreCase);

result= regEx.Replace(text, "<a href=\"/newPage/Index/$1&opid=$2)\">");

"can't get it working" is not very descriptive. What isn't working? Errors? Exceptions? Please post what you expect to happen vs what is happening. — Oded
– Oded, Commented Sep 6, 2012 at 10:01
Very difficult to choose an exact duplicate on the 'related' list. However, don't use Regex, use Html Agility Pack — Steve
– Steve, Commented Sep 6, 2012 at 10:03
What @Steve said, in conjunction with the Uri class to parse the URLs once you get them using the HAP. — Oded
– Oded, Commented Sep 6, 2012 at 10:05
Just to point you in the right direction if you still want to go down the Regex route: Look into escape characters. e.g. ? makes the previous character optional. so ...page.asp?id matches ...page.asid or page.aspid but NOT page.asp?id — RobH
– RobH, Commented Sep 6, 2012 at 11:48

user21926user21926 · Accepted Answer · 2012-09-06 12:51:41Z

1

Everything looks fine except that . and ? are special characters in regular expressions, so they need to be escaped to be treated as literals. So your expression:

string regex = "<a href=\"http://domain/page.asp?id=(\\d+)&amp;oid=(\\d+)&amp;type=(\\w+)\">";

Needs to be:

string regex = "<a href=\"http://domain/page\\.asp\\?id=(\\d+)&amp;oid=(\\d+)&amp;type=(\\w+)\">";

Note the backslashes in front of the . and ?.

answered Sep 6, 2012 at 12:51

user21926

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