Gets a value indicating whether the supplied prefix has a namespace defined for the current pushed scope.
true if there is a namespace defined; otherwise, false.
To determine whether there is a default empty namespace defined, set prefix to String.Empty. A return value of true indicates that there is a default namespace defined in the current scope; false indicates that no default namespace is defined.
xmlns:x= "" is illegal according to the tp://www.w3.org/TR/REC-xml-names/ recommendation.