How to Use XPath with a Default Namespace in C#?

Use the default named space in C#xpath

When processing the XML document containing the default naming space, the XPATH selection node in C#may encounter challenges. This is because Xpath expression usually needs to be explicitly declared the naming space to identify the elements and attributes in the document.

In the example provided, the code attempts to use XPathNavigator to select the node from the XML document with the default named space. However, if you do not specify the name space, you will not have any results.

Solution:

The method of solving this problem is to contain the default named space in the Xpath expression. This can be achieved by using XMLNAMESPACEMANAGER to associate the naming space prefix with URI. The following is the updated code version:

In the code after this update:

<code class="language-csharp">XmlElement el = ...; //TODO
XmlNamespaceManager nsmgr = new XmlNamespaceManager(
    el.OwnerDocument.NameTable);
nsmgr.AddNamespace("x", el.OwnerDocument.DocumentElement.NamespaceURI);
var nodes = el.SelectNodes(@"/x:outerelement/x:innerelement", nsmgr);</code>

Get the reference to the root element (XMLELEMENT EL).

Create a XMLNAMESPACEMANAGER to manage the naming space prefix.
The naming space prefix "X" is mapped into the name space of the document root element URI.
XPath expression now includes the prefix "X" before the element name, which shows the default name space.
• By using the specified naming space prefix, the XPath expression can correctly identify and select the required nodes in the XML document. This method ensures proper consideration and analysis of naming space in the selection process.

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