/// <summary>
        /// Updates the sort expression
        /// </summary>
        public void UpdateSortExpression(string sortExpression)
        {
            SortExpressionParser sep = new SortExpressionParser(SortExpression, SortAscending);

            sep.UpdateSortExpression(sortExpression);

            SortExpression = sep.SortExpression;
            SortAscending  = sep.SortAscending;
        }
        /// <summary>
        /// Gets the list of sort expressions
        /// </summary>
        public List <ISortExpression> GetSortExpressions()
        {
            SortExpressionParser sep = new SortExpressionParser(SortExpression, SortAscending);

            return(sep.GetSortExpressions());
        }