Finding all href values in a HTML string with C# .NET

Say you’d like to collect all link URLs in a HTML text. E.g.:

<html>
   <p>
     <a href=\"http://www.fantasticsite.com\">Visit fantasticsite!</a>
   </p>
   <div>
     <a href=\"http://www.cnn.com\">Read the news</a>
   </div>
</html>

The goal is to find “http://www.fantasticsite.com&#8221; and “http://www.cnn.com&#8221;. Using an XML parser could be a solution if the HTML code is well formatted XML. This is of course not always the case so the dreaded regular expressions provide a viable alternative.

The following code uses a Regex to find those sections in the input text that match a regular expression:

static void Main(string[] args)
{
	string input = "<html><p><a href=\"http://www.fantasticsite.com\">Visit fantasticsite!</a></p><div><a href=\"http://www.cnn.com\">Read the news</a></div></html>";
	FindHrefs(input);
	Console.WriteLine("Main done...");
	Console.ReadKey();
}

private static void FindHrefs(string input)
{
	Regex regex = new Regex("href\\s*=\\s*(?:\"(?<1>[^\"]*)\"|(?<1>\\S+))", RegexOptions.IgnoreCase);
	Match match;
	for (match = regex.Match(input); match.Success; match = match.NextMatch())
	{
		Console.WriteLine("Found a href. Groups: ");
		foreach (Group group in match.Groups)
		{
			Console.WriteLine("Group value: {0}", group);
		}				
	}

}

This gives the following output:

FindHrefs Regexp in action

View all posts related to string and text operations here.

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