What is the REGEX to match this pattern in a html document in C#?

Question

I really can't work out how to best do this, I can do fairly simple regex expressions, but the more complex ones really stump me.

The following appears in specific HTML documents:

<span id="label">
<span>
<a href="http://variableLink"&gt;Joe Bloggs</a>
now using
</span>
<span>
'
<a href="/variableLink/">Important Data</a>
'
</span>
<span>
on
<a href="/variableLink">Important data 2</a>
</span>
</span>

I need to extract the two 'important data' points and could spend hours working out the regex to do it.(I'm using the .net Regex Library in C# 3.5)

Answer 1

As often stated befor, regular expressions are usually not the right tool for parsing HTML, XML, and friends - think about using HTML or XML parsing libraries. If you really want to or have to use regular expressions, the following will match the content of the tags in many cases, but might still fail in some cases.

<a href="[^"]*">(?<data>[^<]*)</a>

This expression will match all links not starting with http:// - this is the only obviouse difference I can see between the links.

<a href="(?!http://)[^"]*"&gt;(?&lt;data&gt;[^&lt;]*)&lt;/a&gt;

Answer 2

Look up look-behind and look-ahead syntax for .NET and use that to look for the anchor tags in the HTML. This site may help you. As an alternative to regular expressions, you might consider using a System.Xml.XPath.XPathNavigator to address those nodes directly.

Answer 3

My Regex is a little rusty but something along the lines of the following may help (although it will probably need some fine-tuning):

(?<=\<a href="/variableLink[/]?"\>)(.*)+(?=</a>)

Answer 4

  <a\shref.*?"/variableLink/?">(.*)</a>

First group contains the Name of the anchors. Tested with Expresso. Works on the sample text you've provided.
Update: works with Snippy too.

Regex regex = new Regex(@"<a\shref.*?""/variableLink/?"">(.*)</a>", RegexOptions.Multiline);
foreach (Match everyMatch in regex.Matches(sText))
{
  Console.WriteLine("{0}", everyMatch.Groups[1]);
}

Outputs:

Important Data
Important data 2

Answer 5

The below uses HtmlAgilityPack. It prints any text within a second-or-later link within the "label" id. Of course, it's relatively simple to modify the XPath to do something a little different.

    HtmlDocument doc = new HtmlDocument();
    doc.Load(new StringReader(@"<span id=""label"">
<span>
<a href=""http://variableLink""&gt;Joe Bloggs</a>
now using
</span>
<span>
'
<a href=""/variableLink/"">Important Data</a>
'
</span>
<span>
on
<a href=""/variableLink"">Important data 2</a>
</span>
</span>
"));
    HtmlNode root = doc.DocumentNode;

    HtmlNodeCollection anchors;
    anchors = root.SelectNodes("//span[@id='label']/span[position()>=2]/a/text()");
    IList<string> importantStrings;
    if(anchors != null)
    {
        importantStrings = new List<string>(anchors.Count);
        foreach(HtmlNode anchor in anchors)
     importantStrings.Add(((HtmlTextNode)anchor).Text);
    }
    else
        importantStrings = new List<string>(0);

    foreach(string s in importantStrings)
        Console.WriteLine(s);