How to get the Namespace string i.e. first element attribute value

I have a namespace declaration/FirstElement like:

<Code>.<FirstElementName xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema-instance" xmlns=urn:filename-schema" </Code>

Which namespace is the attribute for this element? If I wanted to pick up only the last namespace I.e. (xmlns=urn:filename-schema"), how do I do that? I have tried:

<Code>.

Dim root As XmlNode = myDoc.FirstChild. 'First node
Dim firstElement As XmlNode = root.FirstChild. 'First element

Dim firstElementValue As string = firstElement.Value

</Code>

I get the exception: Object reference not set to an instance of an object. I have tried the: XmlAttribute and XmlNode, instances in place of 'String' with no success. Confused now. Please help. Thanks