internal void WriteXml (XmlWriter writer, DiscoveryVersion version)
{
if (writer == null)
throw new ArgumentNullException ("writer");
// standard members
Address.WriteTo (AddressingVersion.WSAddressing10, writer);
// non-standard members
writer.WriteStartElement ("Duration", SerializationNS);
writer.WriteValue (Duration);
writer.WriteEndElement ();
foreach (var ext in Extensions)
ext.WriteTo (writer);
}