public ExpressionParseOnDemand(ParseToConstructDelegate parseToConstruct, string expression)
            : base(expression)
        {
            if (parseToConstruct == null)
                throw new ArgumentNullException();

            this.parseToConstruct = parseToConstruct;
        }
        public ExpressionParseOnDemand(ParseToConstructDelegate parseToConstruct, string expression)
            : base(expression)
        {
            if (parseToConstruct == null)
            {
                throw new ArgumentNullException();
            }

            this.parseToConstruct = parseToConstruct;
        }