HtmlAgilityPack DocumentNode.SelectNodes returns null, shouldn't

问题

I'm trying to scrape content from an example page using the HTML agility pack. The DocumentNode.SelectNodes is returning null for an XPath query when I think it shouldn't. Could someone tell me why? The code is:

HtmlDocument doc = new HtmlDocument();
string xpath = "//h1[@class='product-title fn']"; // note, it still returns 
                                                  // null even with "//div"
doc.OptionFixNestedTags = true;
HtmlNode.ElementsFlags.Remove("form");
HtmlNode.ElementsFlags.Remove("option");

HtmlNodeCollection coll = doc.DocumentNode.SelectNodes(xpath);

if (coll != null)
{
    // do stuff
}
else
{
    // not expecting it to be null unless no matches
}

回答1:

According to the upstream bug comments it is for consistency:

DarthObiwan wrote Jan 11 2011 at 9:27 PM

This has been covered before, this function is written to mimic the way the System.XML works. Doing so will cause a major breaking change and thus will probably be slated for 2.0

• http://htmlagilitypack.codeplex.com/workitem/29175
• http://htmlagilitypack.codeplex.com/workitem/25973

来源：https://stackoverflow.com/questions/8619724/htmlagilitypack-documentnode-selectnodes-returns-null-shouldnt