How can one insert the 'XML Base' attribute/namespace (http://en.wikipedia.org/wiki/XML_Base) into the root of an XElement or XDocument?
<feed xml:base="someurl.com">...</feed>
And, do that without messing up the whole XElement (e.g. by it trying to insert the same everywhere else or some related crazy side effect).
This should do the trick:
element.Root.SetAttributeValue(XNamespace.Xml + "base", "someurl.com")
(Edit: SetAttributeValue)