internal override XElement CreateXml()
{
var xRoot = new XElement(XmlConstants.Brick);
xRoot.SetAttributeValue(XmlConstants.Type, XmlConstants.XmlPlaceAtBrickType);
var xElementY = YPosition.CreateXml();
xElementY.SetAttributeValue(XmlConstants.Category, XmlConstants.YPosition);
var xElementX = XPosition.CreateXml();
xElementX.SetAttributeValue(XmlConstants.Category, XmlConstants.XPosition);
var xFormulalist = new XElement(XmlConstants.FormulaList);
xFormulalist.Add(xElementY);
xFormulalist.Add(xElementX);
xRoot.Add(xFormulalist);
return xRoot;
}