Regex change href="link" to href="notify('link')"

Question

Regex always make me scratching head.

In my Windows Store App, an html content <a href="www.example.com"> need to be replaced to <a href="javascript:window.external.notify('www.example.com')"> in order to intercept Navigation event in WebView.

I tried Regex.Replace(content, "<a href=\"(.+)\">", "<a href=\"javascript:window.external.notify('\\0')\">"); but no luck.

Could you teach me how to do it in C#?

Have your read [**the answer**](http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags) first?... — Alexei Levenkov, Apr 21 '14 at 03:15
@AlexeiLevenkov // Yes, I read many words about *Do NOT parse HTML with Regex*, but my content is not so heavy, so it *would* be fine to treatment in this way. Parsing HTML and Requesting additional memory-burden process is overkill in my case. — Youngjae, Apr 21 '14 at 03:22
@AlexeiLevenkov // Or, I appreciate if you give more appropriate approach to handle my work (with C#). — Youngjae, Apr 21 '14 at 03:23
@Youngjae You mention headscratching with regex. Do you know RegexHero? It's a great tool to try out .Net regex: http://regexhero.net/tester/ — joce, Apr 21 '14 at 04:01
[Obligatory link](http://stackoverflow.com/q/4231382/471272): please link to answer, not to non-answers. — tchrist, Jun 08 '14 at 20:07

joce · Accepted Answer · 2014-04-21T04:30:29.917

This should work for you:

using System;
using System.Text.RegularExpressions;

namespace CSTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Regex re = new Regex("<a href=\"(.+)\">", RegexOptions.Compiled);

            string input = "<a href=\"www.example.com\">";
            string res = re.Replace(input, 
                "<a href=\"javascript:window.external.notify('$1')\">");

            Console.WriteLine(res);
        }
    }
}

You pretty much had it. Your only problem was that you were using \\0 instead of $1 for the matched group.

If you prefer to call the static version of Regex.Replace, you could use:

string res = Regex.Replace(input, 
    "<a href=\"(.+)\">", 
    "<a href=\"javascript:window.external.notify('$1')\">",
    RegexOptions.Compiled
);

grin0048 · Answer 2 · 2014-04-21T04:29:15.423

1

I'd give something like this a try:

Regex.Replace(content, "(?<=<a href=\").+(?=\">)", "javascript:window.external.notify('$0')");

edited Apr 21 '14 at 04:29

answered Apr 21 '14 at 04:18

grin0048

534
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score 0 · Answer 3 · answered Apr 21 '14 at 03:58

0

you should be using $1 instead of \\0.

We use $ for backreferences in c#.

answered Apr 21 '14 at 03:58

aelor

10,892
3
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48

\ is indeed used for backreferences in C#. See http://msdn.microsoft.com/en-us/library/thwdfzxy%28v=vs.110%29.aspx What we're dealing with here is a capture group, which are represented with $: http://msdn.microsoft.com/en-us/library/bs2twtah%28v=vs.110%29.aspx – joce Apr 21 '14 at 04:06
@Joce thts strange , coz I keep getting this error : `prog.cs(14,63): error CS1009: Unrecognized escape sequence `\1' Compilation failed: 1 error(s), 0 warnings` tried here : http://ideone.com/MvgIm4 – aelor Apr 21 '14 at 04:10
you need to use either @"bla bla \1" (raw string) or "bla bla \\1" (escaped backslash). – joce Apr 21 '14 at 04:12
can you edit and save it in another ideone, because when I change it to `\\1` it results to `\1`. – aelor Apr 21 '14 at 04:14
Which I see you do use... FYI, your code compile fine in VS2012: http://i.imgur.com/G2S8dxs.png – joce Apr 21 '14 at 04:14
ooh there seems to be a misunderstanding , see here sir http://ideone.com/MvgIm4 – aelor Apr 21 '14 at 04:16
the above only works if I change the `\\1` to `$1` – aelor Apr 21 '14 at 04:17
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/51071/discussion-between-joce-and-aelor) – joce Apr 21 '14 at 04:17

Regex change href="link" to href="notify('link')"

3 Answers3