Converting URLs Into Links With Regex
/// <summary> /// Finds web and email addresses in a string and surrounds then with the appropriate HTML anchor tags /// </summary> /// <param name="s"></param> /// <returns>String</returns> public static string WithActiveLinks(this string s) { //Finds URLs with no protocol var urlregex = new Regex(@"\b\({0,1}(?<url>(www|ftp)\.[^ ,""\s<)]*)\b", RegexOptions.IgnoreCase | RegexOptions.Compiled); //Finds URLs with a protocol var httpurlregex = new Regex(@"\b\({0,1}(?<url>[^>](http://www\.|http://|https://|ftp://)[^,""\s<)]*)\b", RegexOptions.IgnoreCase | RegexOptions.Compiled); //Finds email addresses var emailregex = new Regex(@"\b(?<mail>[a-zA-Z_0-9.-]+\@[a-zA-Z_0-9.-]+\.\w+)\b", RegexOptions.IgnoreCase | RegexOptions.Compiled); s = urlregex.Replace(s, " <a href=\"http://${url}\" target=\"_blank\">${url}</a>"); s = httpurlregex.Replace(s, " <a href=\"${url}\" target=\"_blank\">${url}</a>"); s = emailregex.Replace(s, "<a href=\"mailto:${mail}\">${mail}</a>"); return s; }
This will convert most URLs, but not all. Parsing URLs is not the easiest thing to do so you need to make a judgement on what type of URLs your users/visitors are most likely to provide and alter the regex patterns accordingly. One thing to point out is that the second pattern (the one that matches URLs with a protocol - http, https etc) also checks to make sure that it isn't already a hyperlink. By the time the second Replace() operations takes place, URLs without protocols will already be fitted with them, and have HTML surrounding them.
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Date Posted:
22 May 2010 22:56
Last Updated:
Posted by:
Mikesdotnetting
Total Views to date:
5791
Comments
04 December 2010 20:02 from Tvrtko
Hello Mike,
this works great, however, part with email link will duplicate anchor tag. For http urls you did ignore existing html anchors from match correctly , but for email they get matched even if they have html anchor around already.