SKUsDetails
is defined in http://tempuri.org/
namespace. You can use this code to select SKUsDetails
using XPath:
var doc = XDocument.Load("1.xml");
var mgr = new XmlNamespaceManager(doc.CreateReader().NameTable);
mgr.AddNamespace("a", "http://tempuri.org/");
var node = doc.XPathSelectElement("//a:SKUsDetails", mgr);
To select SKUDetails
use: //a:SKUsDetails/a:SKUDetails