>https://msdn.microsoft.com/en-us/library/system.xml.xmlnamespacemanager.hasnamespace(v=vs.110).aspx ?

I thought about that but it seems that one is what we have loaded in the XML namespace manager and not as per the XML.

Thinking of it, I do not think it is possible. The only way to resolve this is to trap it in the code. For example, once the namespace loaded, I will look up for a specific node. If that does not work, it would then be either the node does not exist or the namespace was not properly defined.