working with XmlDocument and XDocument

Let say in your code you already have an instance of XmlDocument and you want to manipulate it easily, you can use the XDocument to do that. 

Just for example, let us load an xml from existing file.  
            
            // read the xml
            StreamReader srr = new StreamReader(@"c:\composite.xml");

            // load in XmlDocument
            XmlDocument doc = new XmlDocument();
            doc.Load(srr);

            // create XmlNodeReader
            XmlNodeReader nodereader = new XmlNodeReader(doc);

            // load in XDocument
            XDocument xd = XDocument.Load(nodereader);

            // you can now traverse in its descendants much more easily
            foreach (var x in xd.Descendants())
            {
                if (x.NodeType == XmlNodeType.Element && !x.HasElements)
                {
                    Console.WriteLine("Name:{0}, Value:{1}", x.Name, x.Value);
                    x.SetValue((object)x.Value + "_x");
                }
            }
            
            // save it for comparison
            xd.Save(@"C:\composite_xd.xml", SaveOptions.None);

            // load it back to XmlDocument
            doc.Load(xd.CreateReader());

            // save it for comparison
            doc.Save(@"C:\composite_xmldoc.xml");