XDocument xml = XDocument.Load(@"C:file.xml");
XNamespace xmlns = "http://www.com/namespace";
var vehicles = from vehicle in xml.Descendants(xmlns + "Element")
               select vehicle.Element(xmlns + "Item")
};

public static class XDoncumentExtentions
{
    private static string DefaultNamespace = "{http://schemas.openxmlformats.org/spreadsheetml/2006/main}";
    public static IEnumerable<XElement> DescendantsSimple(this XContainer me, string simpleName)
    {
        return me.Descendants(string.Format("{0}{1}", DefaultNamespace, simpleName));
    }

    public static IEnumerable<XElement> ElementsSimple(this XContainer me, string simpleName)
    {
        return me.Elements(string.Format("{0}{1}", DefaultNamespace, simpleName));
    }

    public static XElement ElementSimple(this XContainer me, string simpleName)
    {
        return me.Element(string.Format("{0}{1}", DefaultNamespace, simpleName));
    }
}