static void ParseValues(XElement el, out int? address, out string unit, out TableType? tableType)
{
address = null;
unit = null;
tableType = null;
XAttribute attr = el.Attribute (X_address);
if (attr != null)
address = ParseHexInt ((string)attr, attr);
attr = el.Attribute (X_tableType);
if (attr != null) {
TableType parsedType;
if (TableTypes.TryParse ((string)attr, out parsedType))
tableType = parsedType;
}
unit = (string)el.Attribute (X_unit);
}