private string WriteFarm(XmlWriter writer, Farm farm)
{
var farmId = farm.Id.FindIsoId() ?? GenerateId();
TaskWriter.Ids.Add(farmId, farm.Id);
writer.WriteStartElement(XmlPrefix);
writer.WriteAttributeString("A", farmId);
writer.WriteAttributeString("B", farm.Description);
WriteContactInfo(writer, farm.ContactInfo);
WriteCustomerReference(writer, farm.GrowerId);
writer.WriteEndElement();
return farmId;
}