private TreatmentZone LoadTreatmentZone(XmlNode inputNode, out int zoneId)
{
// Required fields. Do not proceed if they are missing
if (!inputNode.GetXmlNodeValue("@A").ParseValue(out zoneId))
return null;
// Optional fields
var zone = new TreatmentZone { Variables = new List<DataVariable>() };
zone.Name = inputNode.GetXmlNodeValue("@B");
LoadDataVariables(inputNode.SelectNodes("PDV"), zone);
return zone;
}