ASP.NETMVC4 分页组合查询解决方法

本人新手刚在webform转到mvc   像linq  ef啥的，都是不会的不行不行的，不会就问群友，找资料

今天本屌遇到了一个分页组合查询的问题，解决了2个小时，把代码共享给大家

话不多话，直接上代码，理论上的东东我就不描述，初中没毕业文化太低也描述不了

新建一个表达式数的操作类

public static class PredicateBuilder
    {

        public static Expression<Func<T, bool>> True<T>() { return f => true; }
        public static Expression<Func<T, bool>> False<T>() { return f => false; }
        public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
        {
            // build parameter map (from parameters of second to parameters of first)
            var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);

            // replace parameters in the second lambda expression with parameters from the first
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

            // apply composition of lambda expression bodies to parameters from the first expression
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

        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);
        }

        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);
        }
    }

    public class ParameterRebinder : ExpressionVisitor
    {
        private readonly Dictionary<ParameterExpression, ParameterExpression> map;

        public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
        {
            this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
        }

        public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
        {
            return new ParameterRebinder(map).Visit(exp);
        }

        protected override Expression VisitParameter(ParameterExpression p)
        {
            ParameterExpression replacement;
            if (map.TryGetValue(p, out replacement))
            {
                p = replacement;
            }
            return base.VisitParameter(p);
        }
    }  

基本的做好，下一步就是调用了

代码  下看

//获取页容量
            int pageSize = FytRequest.GetFormInt("rows", );
            //获取请求的页码
            int pageIndex = FytRequest.GetFormInt("page", );
            var key = FytRequest.GetFormStringEncode("key");
            int statu = FytRequest.GetFormInt("statu");
            var begintime = FytRequest.GetFormString("begintime");
            var endtime = FytRequest.GetFormString("endtime");
            var where = PredicateBuilder.True<tb_SystemLog>();
            #region 组合查询
            if (key!="")
            {
                where = where.And(m => m.loginName.Contains(key));
                where = where.Or(m=>m.title.Contains(key));
            }
            if (statu!=-)
            {
                where = where.And(m=>m.logType==statu);
            }
            if (begintime != "" && endtime != "")
            {
                var bt = Convert.ToDateTime(begintime);
                var et = Convert.ToDateTime(endtime);
                where = where.And(m => m.addDate >= bt && m.addDate <= et);
            }
            #endregion
            var dataList = OperateContext.BLLSession.Itb_SystemLogBLL.GetPagedList(pageIndex, pageSize, where, p => p.ID);
            int rowCount = OperateContext.BLLSession.Itb_SystemLogBLL.GetListBy(where).Count();
            var jsonM = new JsonHelper.JsonAjaxModel()
            {
                Data = dataList,
                PageTotal = ,
                Status = "ok"
            };

ok好了，这样就可以用了，我这个分页内部是接口做的，

爽来的，我把分页实现也分享给大家，

#region 6.0 分页查询 + List<T> GetPagedList<TKey>
        /// <summary>
        /// 6.0 分页查询 + List<T> GetPagedList<TKey>
        /// </summary>
        /// <param name="pageIndex">页码</param>
        /// <param name="pageSize">页容量</param>
        /// <param name="whereLambda">条件 lambda表达式</param>
        /// <param name="orderBy">排序 lambda表达式</param>
        /// <returns></returns>
        public List<T> GetPagedList<TKey>(int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, Expression<Func<T, TKey>> orderBy)
        {
            // 分页 一定注意： Skip 之前一定要 OrderBy
            return whereLambda == null ?
                db.Set<T>().OrderBy(orderBy).Skip((pageIndex - ) * pageSize).Take(pageSize).ToList() :
                db.Set<T>().Where(whereLambda).OrderBy(orderBy).Skip((pageIndex - ) * pageSize).Take(pageSize).ToList();
        }

        #endregion

有些人可能看代码很熟悉，就不要拆穿了，你懂得

交流：86594082 有事情可以找我哈，共同学习