XMLNamespaceManager and Default Namespaces
I was working with using the XMLNamespaceManager object the other day, and saw that there was a DefaultNamespace property, but it wasn't assignable. In doing some research, it turns out that if you want to assign a default namespace, you call AddNamespace with a string.Empty value for the first argument, and the default namespace for the second. This would be done as such:
objManager.AddNamespace(string.Empty, "http://someuri.com/myschema");
This adds a default namespace to the manager, and provides the value through the DefaultNamespace property.