C# parse html with xpath

问题

I'm trying to parse out stock exchange information whit a simple piece of C# from a HTML document. The problem is that I can not get my head around the syntax, the tr class="LomakeTaustaVari" gets parsed out but how do I get the second bit that has no tr-class?

Here's a piece of the HTML, it repeats it self whit different values.

<tr class="LomakeTaustaVari">
    <td><div class="Ensimmainen">12:09</div></td>
    <td><div>MSI</div></td>
    <td><div>POH</div></td>
    <td><div>42</div></td>
    <td><div>64,50</div></td>
</tr>
<tr>
    <td><div class="Ensimmainen">12:09</div></td>
    <td><div>SRE</div></td>
    <td><div>POH</div></td>
    <td><div>156</div></td>
    <td><div>64,50</div></td>
</tr>

My C# code:

{
    HtmlAgilityPack.HtmlWeb web = new HtmlWeb();
    HtmlAgilityPack.HtmlDocument doc = web.Load ("https://www.op.fi/op/henkiloasiakkaat/saastot-ja-sijoitukset/kurssit-ja-markkinat/markkinat?sivu=alltrades.html&sym=KNEBV.HSE&from=10:00&to=19:00&id=32453");

    foreach (HtmlNode row in doc.DocumentNode.SelectNodes("//tr[@class='LomakeTaustaVari']")) 
    {
        Console.WriteLine(row.InnerText);     
    }
    Console.ReadKey();
}

回答1:

Try to use the next xpath //tr[preceding-sibling::tr[@class='LomakeTaustaVari']]:

var nodes = doc.DocumentNode.SelectNodes("//tr[preceding-sibling::tr[@class='LomakeTaustaVari']]");

It should select nodes that have preceding node tr with class LomakeTaustaVari.

Just FYI: if no nodes found, SelectNodes method returns null.

回答2:

If you manage to get a reference to the <tr class="LomakeTaustaVari"> element, I see two possible solutions.

You can navigate to the parent and then find all its <tr> children:

lomakeTaustaVariElement.Parent.SelectNodes("tr"); // iterate over these if needed

You can also use NextSibling to get the next <tr>:

var trWithoutClass = lomakeTaustaVariElement.NextSibling;

Please note that using the second alternative you may run into issues, because whitespace present in the HTML may be interpreted as being a distinct element.

To overcome this, you may recursively call NextSibling until you encounter a tr element.

回答3:

This will iterate over all nodes in document. You will probably also need to be more specific with starting node, so you will only select that you are interested in.

foreach (HtmlNode row in doc.DocumentNode.SelectNodes("//tr")) 
{
    Console.WriteLine(row.InnerText);     
}

回答4:

Probably I don't understand something, but the simplest XPath for any tr element selection should do the work:

doc.DocumentNode.SelectNodes("//tr")

Otherwise, in case you would like to select elements with specific class attributes only, it could be:

doc.DocumentNode.SelectNodes("//tr[@class = 'someClass1' or @class = 'someClass2']")

来源：https://stackoverflow.com/questions/19405264/c-sharp-parse-html-with-xpath

标签

xpath

html-agility-pack