public static void Main()
Expression taxExpr = new Expression("IF(LOWER(TAX_CODE)='vat',amount*10/100,IF(LOWER(TAX_CODE)='gst',amount*15/100,0))");
taxExpr.Bind("TAX_CODE","GST");
taxExpr.Bind("amount", 5005m);
Decimal value = taxExpr.Eval<Decimal>();
Console.WriteLine(value);