internal override void LoadFromXml(XElement xRoot)
{
if(xRoot.Element(XmlConstants.LeftChild) != null)
LeftChild = new XmlFormulaTree(xRoot.Element(XmlConstants.LeftChild));
if (xRoot.Element(XmlConstants.RightChild) != null)
RightChild = new XmlFormulaTree(xRoot.Element(XmlConstants.RightChild));
if (xRoot.Element(XmlConstants.Type) != null)
VariableType = xRoot.Element(XmlConstants.Type).Value;
if (xRoot.Element(XmlConstants.Value) != null)
VariableValue = xRoot.Element(XmlConstants.Value).Value;
}