Regex replace value with first match

Question

I was wondering if something like this is possible with Regex, to replace a value ('John Doe' in my example below) with the first match ('[email protected]' in my example below):

Input:

Contact: <a href="mailto:[email protected]">John Doe</a>

Output:

Contact: [email protected]

Thanks in advance.

Yes, it is possible. however, your example is not clear. which part do you replace with what? As far as I can see, you just match and return some part of the string, there is no replace. — Ali Ferhat
– Ali Ferhat, Commented Mar 10, 2012 at 9:45
@AliFerhat I want to replace the name (John Doe) with the email address. — Nick
– Nick, Commented Mar 10, 2012 at 10:15

kyrylomyr · Accepted Answer · 2012-03-10 10:48:48Z

1

It would be something like this. The code will replace names with e-mails in all mailto links:

var html = new StringBuilder("Contact: <a href=\"mailto:[email protected]\">John1 Doe1</a> <a href=\"mailto:[email protected]\">John2 Doe2</a>");

var regex = new Regex(@"\<a href=\""mailto:(?<email>.*?)\""\>(?<name>.*?)\</a\>");
var matches = regex.Matches(html.ToString());

foreach (Match match in matches)
{
    var oldLink = match.Value;
    var email = match.Groups["email"].Value;
    var name = match.Groups["name"].Value;
    var newLink = oldLink.Replace(name, email);
    html = html.Replace(oldLink, newLink);
}

Console.WriteLine(html);

Output:

Contact: <a href="mailto:[email protected]">[email protected]</a> <a href="mailto:[email protected]">[email protected]</a>

edited Mar 10, 2012 at 10:48

answered Mar 10, 2012 at 10:04

kyrylomyr

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3 Comments

Nick Over a year ago

Unfortunately, I do need to "inject" the match rather than construct a new string, because the input is a large string with more text beyond what I've specified in the example.

kyrylomyr Over a year ago

@Nick, am I right understand that you have an HTML-page that can contain many "mailto" links and you want to replace them all?

jCoder Over a year ago

If the HTML page is stored in a string object, then there is little chance to "inject", as the MSDN notes Strings are immutable--the contents of a string object cannot be changed after the object is created. Depending on how the HTML data is retrieved, you might consider a different approach.

Nick · Accepted Answer · 2012-03-11 06:15:09Z

0

Ok, got it working using MatchEvaluator delegate and named captures:

output = Regex.Replace(input, 
    @"\<a([^>]+)href\=.?mailto\:(?<mailto>[^""'>]+).?([^>]*)\>(?<mailtext>.*?)\<\/a\>", 
    m => m.Groups["mailto"].Value);

answered Mar 11, 2012 at 6:15

Nick

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