Html Agility Pack C#

Question

I’d like to know how the // in the Html Agility Pack. Well, the doubt is the following, code:

var t = htmlDoc.DocumentNode.SelectNodes("//table[@class='" + attr + "']").First().SelectNodes("tbody").First()
                    .SelectNodes("tr");

int index = 0;

Empresa empresa = new Empresa();

foreach (var elem in t)
{
    var tdList = elem.SelectNodes("td");
    foreach (var td in tdList)
    {
        if (td.HasClass("higher"))
        {
            index++;
            empresa = new Empresa();
            empresa.nome = td.InnerText.Trim();
        }
        else if (td.HasClass("strong"))
        {
            empresa.nro = index;
            Siglas sigla = new Siglas();
            sigla.Sigla = td.InnerText.Trim();
            sigla.link = td.SelectNodes("a").First().GetAttributeValue("href", "");
            empresa.siglas.Add(sigla);
        }

        if (td == tdList.Last())
            listEmpresa.Add(empresa);
    }
}

On the part that I’m getting the table, if I put

(Without the //)

htmlDoc.DocumentNode.SelectNodes("table[@class='" + attr + "']").First()

It does not bring any object to my list, until then ok, I understood that there // are necessary.

Already in the part I try to catch the href of the tag a

(With //)

sigla.link = td.SelectNodes("//a").First().GetAttributeValue("href", "");

example of caught link = "www.google.com"

(Without //)

sigla.link = td.SelectNodes("a").First().GetAttributeValue("href", "");

example of caught link = "www.google.com/xxxx-xxxx"

Well, my question is as follows. Why I can get the full address of href only if I use without the // ? How does the // in that library? I’ve seen it too .// I’m not sure how it works either. I was able to do what I wanted to get the full address of the "a" tag, but I would like to understand what I did.

Answer 1

Ola. The Xpath is a query language to easily select nodes in the Mark language such as xml itself.

Follow a descriptive of the language that can help you understand more. https://www.w3schools.com/xml/xml_xpath.asp

a good tool based on HAP to test/discover the Xpath paths that the HAP itself will understand: https://github.com/samfisher83/HTML-Agility-xpath-finder