private ValuePresentation LoadUnit(XmlNode inputNode, out string unitId)
{
var unit = new ValuePresentation();
// Required fields. Do not proceed if they are missing
unitId = inputNode.GetXmlNodeValue("@A");
if (string.IsNullOrEmpty(unitId) ||
!LoadRequiredFields(inputNode, unit))
return null;
// Optional fields
unit.Symbol = inputNode.GetXmlNodeValue("@E");
_taskDocument.LoadLinkedIds(unitId, unit.Id);
return unit;
}