Question

Hi there I’ve just registered on this website, because I need some help.

I want to get results from the nyaa.eu website.

Basically:

• Table Node is called <table class="tlist">
• Every row node is called <tr class="tlistrow"> also sometimes it’s ‘trusted tlistrow’ etc.
• The Nodes I try to retrieve are: <td class="tlistname"> <td class="tlistsize"> <td class="tlistsn"> and <td class="tlistln">

Firstly I’m retrieving a table which contains all the info about torrents:

HtmlNode hnTable = doc.DocumentNode.SelectSingleNode("//table[@class='tlist']");

So, next thing is retrieving all the rows which contains ‘tlistrow’ in its class attribute:

HtmlNodeCollection hncRows = hnTable.SelectNodes("//tr[contains(@class,'tlistrow')]");

And finally the problem is when I read every node it’s always the same one:

foreach (HtmlNode row in hncRows)
{
    foreach (HtmlNode child in row.ChildNodes)
    {
        if (child.SelectSingleNode("//td[@class='tlistname']") != null)
        {
            MessageBox.Show("Something found!\n\n" + child.SelectSingleNode("//td[@class='tlistname']").InnerText);
            break;
        }
    }
}

The text displayed in the messagebox is always the same, it looks like it only selects one node multiple times.

How can I fix this or if I am doing anything wrong, please correct me.

Answer 1

    foreach (HtmlNode child in row.ChildNodes)
    {
        if (child.SelectSingleNode("//td[@class='tlistname']") != null)
        {
            MessageBox.Show("Something found!\n\n" + child.SelectSingleNode("//td[@class='tlistname']").InnerText);
            break;
        }
    }

You need to understand the difference between relative XPath expressions and absolute XPath expressions.

A relative XPath expression is evaluated off (having as an initial context node) a specific node in the XML document.

An absolute XPath expression is evaluated against the whole XML document (having as initial context node the document-node).

Any XPath expression that starts with the character / is an absolute XPath expression.

Based on the provided code, you want to use a relative XPath expression with an initial context node, containd in the variable named child.

The problem is that the expression you are using:

//td[@class='tlistname'] 

starts with / and is therefore an absolute XPath expression.

This, passed to the SelectSingleNode() method always selects the first td element in the whole XML document, that has a class attribute with string value "tlistname."

Solution: Use a relative XPath expression, such as:

.//td[@class='tlistname']