Q:

Adding a namespace to existing XDocument

I need to manipulate some xml files using Linq to xml.
I have an existing XDocument that I Load
Now I cannot seem to be able to add a namespace to it.
I do:
//Load an existing xml into a XDocument
XDocument xdoc=XDocument.Load(myXml);

//Create a namespace
 XNamespace myNS="http://www.w3.org/2001/XMLSchema-instance/MyShinyNewNamespace";
 xAttribute myAttr=new XAttribute(XNamespace.Xmlns +"myNS",myNS);

  //Add new namepsace to root

 xdoc.Root ????

What do you do here?

How do I retrieve my namespace?
How do I Remove/Replace?
many thanks

A:

First of all, while XML markup allows you to use
<root xmlns="http://example.com/ns">
  <foo>
    <bar>baz</bar>
  </foo>
</root>

to use a single namespace declaration attribute to put the root element as well as those descendant elements into the declared namespace, when you manipulate the tree model you need to change the Name of all elements so you need e.g.
XNamespace myNs = "http://example.com/ns";

foreach (XElement el in xdoc.Descendants()) 
{
  el.Name = myNs + el.Name.LocalName;
}

If you also want to set a certain prefix pf then addionally set
  xdoc.Root.Add(new XAttribute(XNamespace.Xmlns + "pf", myNs));

