public static WhereClip operator <=(ExpressionClip left, ExpressionClip right)
        {
            WhereClip where = new WhereClip();
            if (ExpressionClip.IsNullOrEmpty(right))
            {
                where = ExpressionFactory.AppendWhereAnd(where, left, QueryOperator.LessOrEqual, null);
            }
            else if (ExpressionClip.IsNullOrEmpty(left))
            {
                where = ExpressionFactory.AppendWhereAnd(where, right, QueryOperator.GreaterOrEqual, null);
            }
            else
            {
                ExpressionFactory.AppendWhereAnd(where, left, QueryOperator.LessOrEqual, right);
            }

            return(where);
        }
        public static ExpressionClip CreateCloneExpression(ExpressionClip expr)
        {
            Check.Require(!ExpressionClip.IsNullOrEmpty(expr));

            return((ExpressionClip)expr.Clone());
        }