Add namespace and alias to existing xml

Question

I am using the code below to change a namespace in an existing XML message in a BizTalk pipeline component. This works but how would I add a namespace alias to the document as well.

XNamespace toNs = "http://hl7.org/fhir/Encounters";

XElement doc = XElement.Parse(xmlIn);

doc.DescendantsAndSelf().Attributes().Where(a => a.IsNamespaceDeclaration).Remove();

var ele = doc.DescendantsAndSelf();

foreach (var el in ele)
    el.Name = toNs +  el.Name.LocalName;

return new XDocument(doc);

Answer 1

You can simply add a declaration attribute to the root. Take this example:

<Root>
    <Child>Value</Child>
</Root>

If you run this code:

var root = XElement.Parse(xml);

XNamespace ns = "http://www.example.com/";

foreach (var element in root.DescendantsAndSelf())
{
    element.Name = ns + element.Name.LocalName;
}

root.Add(new XAttribute(XNamespace.Xmlns + "ex", ns));

You'll get this result:

<ex:Root xmlns:ex="http://www.example.com/">
  <ex:Child>Value</ex:Child>
</ex:Root>

See this fiddle for a demo.