var clients = xml.XPathSelectElements ( “client/child” );
Consider, if required ,an XPathSelectElements overload with namespace management.
Note, that XPath extensions are actually backward compatibility feature, and Microsoft recommends to use native XElement methods, such as Descendants ,Elements,Element etc. See Comparison of XPath and LINQ to XML
However K. Scott Allen prefers to mix LINQ and XPath to have concise code.
See also Concepts LINQ to XML for XPath Users