I'm not familiar with F#, but here is the C# equivalent:

HtmlDocument doc = LoadMyDocument();

foreach (HtmlNode tr in doc.DocumentNode.SelectNodes("tr"))
{
    string title = null;
    HtmlNode titleNode = tr.SelectSingleNode(".//p");
    if (titleNode != null)
    {
        title = titleNode.GetAttributeValue("title", null);
    }

    string anchor = null;
    HtmlNode anchorNode = tr.SelectSingleNode(".//a");
    if (anchorNode != null)
    {
        anchor = anchorNode.InnerText;
    }

    string value = null;
    HtmlNode valueNode = tr.SelectSingleNode("td[last()]");
    if (valueNode != null)
    {
        value = valueNode.InnerText.Trim();
    }

    Console.WriteLine("title=" + title);
    Console.WriteLine("anchor=" + anchor);
    Console.WriteLine("value=" + value);
}

The main problem you have is because you use a "//p" expression which starts off root, instead of a ".//p" which starts from the current node.