XDocument get and set values in XML nodes

Question

I have this XML

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
<S:Header>
<wss:Security xmlns:wss="http://schemas.xmlsoap.org/ws/2002/12/secext">
<wss:UsernameToken>
<wss:Username>username</wss:Username>
<wss:Password>password</wss:Password>
<wss:Nonce></wss:Nonce>
<wss:Created></wss:Created>
</wss:UsernameToken>
</wss:Security>
</S:Header>
<S:Body>
<TaxRegistrationNumber>213213123</TaxRegistrationNumber>
<CompanyName>sadsadasd</CompanyName>
</S:Body>
</S:Envelope>


I want to accesses to the value of <wss:Username> and set a value in <wss:Nonce> node.

I already try 3 ways to get value of <wss:Username> on C# project:

First:
XDocument xmlFile = XDocument.Load(xmlpathfile);
XmlNamespaceManager ns = new XmlNamespaceManager(new NameTable());
ns.AddNamespace("wss", "http://schemas.xmlsoap.org/ws/2002/12/secext/");
XElement UserFinanc = xmlFile.XPathSelectElement("wss:Security/wss:UsernameToken/wss:Username", ns);

Second:
XDocument xmlFile = XDocument.Load(xmlpathfile);
XmlNamespaceManager ns = new XmlNamespaceManager(new NameTable());
var element = xmlFile.Descendants(wss + "Security").Descendants(wss + "UsernameToken").Where(x => x.Descendants(wss + "Username").Any(y => y.Value != "")).First().Element(wss + "UsernameToken");
if (element != null)
MessageBox.Show(element.Element(wss + "Username").Value).Value);

Third:
string grandChild = (string) (from el in xmlFile.Descendants(wss + "Username") select el).First();
MsgBox.Show(grandChild);

I always have similar errors like 'The sequence contains no elements'

Answer 1

Your first attempt is almost right. There are a couple things missing:

1. The namespace defined in code must be an exact match to the one in the xml. In your case the namespace in code has an extra trailing slash. It should be http://schemas.xmlsoap.org/ws/2002/12/secext .
2. The XPath expression should be //wss:Security/wss:UsernameToken/wss:Username . The leading slashes basically mean "look for this node anywhere". Alternatively, you could write out the whole path begining with <S:Envelope> . You would need to add the soap envelope namespace to your code as well.