internal override XElement CreateXml()
{
var xRoot = new XElement(XmlConstants.Brick);
xRoot.SetAttributeValue(XmlConstants.Type, XmlConstants.XmlChangeVolumeByBricksType);
var xElement = VolumeXML.CreateXml();
xElement.SetAttributeValue(XmlConstants.Category, XmlConstants.VolumeChange);
var xFormulalist = new XElement(XmlConstants.FormulaList);
xFormulalist.Add(xElement);
xRoot.Add(xFormulalist);
return xRoot;
}