Expression拼接

public static  class expressionhelp
    {
        /// <summary>
        /// lambda表达式拼接
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <param name="merge"></param>
        /// <returns></returns>
        public static expression<t> compose<t>(this expression<t> first, expression<t> second, func<expression, expression, expression> merge)
        {
            var map = first.parameters.select((f, i) => new { f, s = second.parameters[i] }).todictionary(p => p.s, p => p.f);
            var secondbody = parameterrebinder.replaceparameters(map, second.body);
            return expression.lambda<t>(merge(first.body, secondbody), first.parameters);
        }
        /// <summary>
        /// and扩展
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <returns></returns>
        public static expression<func<t1, t2, bool>> and<t1, t2>(this expression<func<t1, t2, bool>> first, expression<func<t1, t2, bool>> second)
        {
            return first.compose(second, expression.and);
        }
        public static expression<func<t, bool>> and<t>(this expression<func<t, bool>> first, expression<func<t, bool>> second)
        {
            return first.compose(second, expression.and);
        }

        /// <summary>
        /// or扩展
        /// </summary>
        /// <typeparam name="t"></typeparam>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <returns></returns>
        public static expression<func<t1, t2, bool>> or<t1, t2>(this expression<func<t1, t2, bool>> first, expression<func<t1, t2, bool>> second)
        {
            return first.compose(second, expression.or);
        }
        public static expression<func<t, bool>> or<t>(this expression<func<t, bool>> first, expression<func<t, bool>> second)
        {
            return first.compose(second, expression.or);
        }

    }