How to find nodes in an XML

I have loaded the following XML file using xml.Load("myfile.xml"); where xml is of type XmlDocument:

<?xml version="1.0" encoding="ISO-8859-1"?>
    <DTE xmlns="http://www.sii.cl/SiiDte" version="1.0">
        <Documento ID="E000000005T033F0114525415">
            <Encabezado>
                <IdDoc>
                    <TipoDTE>33</TipoDTE>
                    <Folio>114525415</Folio>
                    <FchEmis>2021-11-02</FchEmis>
                    <FmaPago>1</FmaPago>
                    <FchVenc>2021-11-02</FchVenc>
                </IdDoc>
            </Encabezado>
        </Documento>
    </DTE>

How can I get Folionode?

I have tried with:

  xml.DocumentElement.SelectSingleNode("/DTE/Documento/Encabezado/IdDoc/Folio");
  xml.DocumentElement.SelectNodes("DTE/Documento/Encabezado/IdDoc/Folio")
  xml.DocumentElement.SelectSingleNode("//DTE/Documento/Encabezado/IdDoc/Folio");
  xml.DocumentElement.SelectSingleNode("/Documento/Encabezado/IdDoc/Folio");
  xml.DocumentElement.SelectSingleNode("Documento/Encabezado/IdDoc/Folio");
  xml.DocumentElement.SelectSingleNode("/Encabezado/IdDoc/Folio");
  xml.DocumentElement.SelectNodes("/DTE/Documento/Encabezado/IdDoc/Folio")

when I debug xml.DocumentElement I see that the element is DTE so I think xml.DocumentElement.SelectSingleNode("Documento/Encabezado/IdDoc/Folio") should do it.

When I get xml.DocumentElement.FirstChild I get Documento node.

With xml.DocumentElement.FirstChild.FirstChild I get Encabezado node.

With xml.DocumentElement.FirstChild.FirstChild.FirstChild I get IdDoc node.

If I use xml.DocumentElement.FirstChild.FirstChild.FirstChild.SelectSingleNode("Folio"), returned value is null.

If I use xml.DocumentElement.FirstChild.FirstChild.FirstChild.ChildNodes, I get the 5 elements.

Then I could use xml.DocumentElement.FirstChild.FirstChild.FirstChild.ChildNodes[1].InnerText to get Folio value.

I can traverse the XML but, how can I do it to get the element directly?

Thanks Jaime

Solution

It is better to use LINQ to XML API for your task. It is available in the .Net Framework since 2007.

The provided XML has a default namespace. It needs to be declared and used, otherwise it is imposable to find any XML element.

void Main()
{
    const string filename = @"e:\Temp\jstuardo.xml";

    XDocument xdoc = XDocument.Load(filename);
    XNamespace ns = xdoc.Root.GetDefaultNamespace();

    string Folio = xdoc.Descendants(ns + "Folio")
      .FirstOrDefault()?.Value;

    Console.WriteLine("Folio='{0}'", Folio);
}

Output

Folio='114525415'