Question

I have an HTML document opened in two windows, and I need the selected node to be synchronized between both windows.

Using Html Agility Pack I tried:

HtmlNode myNode = GetSomeCertainNode();

string xpath = myNode.XPath; //xpath = "/#comment[1]"

// This line throws an XPathException
var reExtract = myNode.OwnerDocument.DocumentNode.SelectSingleNode(xpath);

Exception message: '/#comment[1]' has an invalid token.

I’m wondering, I took the XPath from the node itself, which means it’s a proper XPath, and I use it against the same document, why does it fail, what do I miss?

Update

When selecting some other nodes I get this exception instead: Expression must evaluate to a node-set. (xpath contains /html[1]/body[1]/div[1]/p[3]/strong[1]/#text[1]).

But remember that the value is taken from the node itself, therefore it’s very weird. How come it’s complaining that it’s invalid?

Answer 1

The # character is illegal in an element name. A valid XPath expression that selects a comment would be /comment()[1]