XElement.GetPrefixOfNamespace gets the prefix associated with a namespace for this XElement.
Imports <xmlns:aw="http://www.domain.com">
Module Module1
Sub Main()
Dim xmlTree As XElement = <aw:Root/>
Dim prefix As String = xmlTree.GetPrefixOfNamespace("http://www.domain.com")
Console.WriteLine("Prefix: {0}", prefix)
End Sub
End Module