public void WriteXml(XmlWriter writer)
        {
            writer.WriteAttributeString("Omschrijving", Omschrijving);
            foreach (Ruimte r in Children)
            {
                writer.WriteStartElement("Ruimte");
                r.WriteXml(writer);
                writer.WriteEndElement();
            }

            var list = Acumulator.Instance().BB.MakeCompleteList();

            if (list.Count > 0)
            {
                writer.WriteStartElement("CompleetLijst");
                int cntr = 0;
                foreach (string c in list)
                {
                    writer.WriteAttributeString("C" + cntr.ToString(), c);
                    cntr++;
                }
                writer.WriteAttributeString("Count", cntr.ToString());
                writer.WriteEndElement();
            }
            if (Korting != null)
            {
                writer.WriteStartElement("KortingInfo");
                Korting.WriteXml(writer);
                writer.WriteEndElement();
            }
        }