How Can I Use XPath with a Default Namespace in C# to Select Nodes?

Navigating XML with Default Namespaces in C# using XPath

Working with XML documents containing default namespaces often requires careful handling of XPath expressions to correctly select nodes. A common mistake is omitting namespace prefixes, leading to empty result sets.

This issue is resolved by explicitly incorporating the namespace into your XPath query. While an XPathNavigator isn't strictly required, the SelectNodes or SelectSingleNode methods are sufficient.

The crucial step is creating an XmlNamespaceManager. The following example demonstrates this:

XmlElement el = ...; //TODO:  Obtain your XmlElement
XmlNamespaceManager nsmgr = new XmlNamespaceManager(el.OwnerDocument.NameTable);
nsmgr.AddNamespace("x", el.OwnerDocument.DocumentElement.NamespaceURI);
var nodes = el.SelectNodes("/x:outerelement/x:innerelement", nsmgr);

This code snippet first initializes an XmlNamespaceManager using the NameTable from the XML document's root. It then registers the default namespace of the root element with the prefix "x". Finally, SelectNodes is called with the XPath expression now including the "x" prefix, enabling the selection of the target nodes. Remember to replace the //TODO comment with the code to obtain your XmlElement.

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