[CODE]
'funzione che aggiorna il valore dell'attributo attr del nodo di nome nodo
  Public Function updateNodo(ByVal padre As String, ByVal nodo As String, ByVal attr As String, ByVal newval As String) As String
    Dim reader As System.Xml.XmlTextReader
    Dim doc As XmlDocument
    Dim node, a, b As XmlNode
    Try
      Dim modified As Boolean = False
      doc = New XmlDocument
      doc.Load(path)
      Dim root As XmlElement = doc.DocumentElement
      node = root.SelectSingleNode(nodo)
      Dim str As String
      For Each a In root.ChildNodes
        If a.Name.Equals(padre) Then
          node = a
          For Each b In node.ChildNodes
            If b.Name.Equals(nodo) Then
              b.Attributes(attr).Value = newval
              modified = True
            End If
          Next
        End If
      Next
      If modified Then
        doc.Save("temp.xml")
        System.IO.File.Copy("temp.xml", path, True)
        Return "OK"
      Else
        'non salvo x' non c'è stata nessuna modifica
        Return "Nodo non trovato"
      End If
    Catch ex As Exception
      If String.Compare(ex.Message, "Elemento di primo livello mancante.") = 0 Then
        Return "File xml vuoto"
      Else
        Return ex.Message
      End If
    Finally
      doc = Nothing
    End Try
  End Function

[/CODE]