【WH】MVC数据分页扩展类

 public static class QueryableExtensions
    {
        #region 内存分页

        /// <summary>
        /// 返回对象分页列表
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="dataSource">已排序的数据源</param>
        /// <param name="pageIndex">页码，1开始</param>
        /// <param name="pageSize">页条数</param>
        /// <returns>对象分页列表</returns>
        public static IPagedList<T> ToPagedList<T>(this IList<T> dataSource, int pageIndex, int pageSize)
            where T : class
        {
            pageIndex = pageIndex <= 0 ? 1 : pageIndex;
            var pagedList = new PagedList<T>
            {
                PageIndex = pageIndex,
                PageSize = pageSize,
                TotalCount = dataSource.Count,
                Entities = dataSource.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList()
            };

            return pagedList;
        }

        /// <summary>
        /// 返回对象分页列表
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="dataSource">已排序的数据源</param>
        /// <param name="pager">分页器对象；当为空时，分页器取默认值</param>
        /// <returns>对象分页列表</returns>
        public static IPagedList<T> ToPagedList<T>(this IList<T> dataSource, Pager pager) where T : class
        {
            pager = pager ?? new Pager();
            return dataSource.ToPagedList(pager.PageIndex, pager.PageSize);
        }

        #endregion

        #region IQueryable分页

        /// <summary>
        /// 返回对象分页列表
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="dataSource">已排序的数据源</param>
        /// <param name="pageIndex">页码，1开始</param>
        /// <param name="pageSize">页条数</param>
        /// <returns>对象分页列表</returns>
        public static IPagedList<T> ToPagedList<T>(this IQueryable<T> dataSource, int pageIndex, int pageSize)
            where T : class
        {
            pageIndex = pageIndex <= 0 ? 1 : pageIndex;
            var pagedList = new PagedList<T>
            {
                PageIndex = pageIndex,
                PageSize = pageSize,
                TotalCount = dataSource.Count(),
                Entities = dataSource.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList()
            };

            return pagedList;
        }

        /// <summary>
        /// 返回对象分页列表
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="dataSource">已排序的数据源</param>
        /// <param name="pager">分页器对象；当为空时，分页器取默认值</param>
        /// <returns>对象分页列表</returns>
        public static IPagedList<T> ToPagedList<T>(this IQueryable<T> dataSource, Pager pager) where T : class
        {
            pager = pager ?? new Pager();
            return dataSource.ToPagedList(pager.PageIndex, pager.PageSize);
        }

        #endregion

        /// <summary>
        /// 当满足特定条件时执行查询
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="source">查询对象</param>
        /// <param name="condition">需要满足的条件</param>
        /// <param name="predicate">满足条件时执行的查询表达式</param>
        /// <returns>结果集</returns>
        public static IQueryable<T> WhereIf<T>(this IQueryable<T> source, bool condition,
            Expression<Func<T, bool>> predicate)
        {
            return condition ? source.Where(predicate) : source;
        }
    }

 /// <summary>
    /// 分页器
    /// </summary>
    public class Pager
    {
        /// <summary>
        /// 分页索引（默认为1）
        /// </summary>
        public int PageIndex { get; set; } = 1;

        /// <summary>
        /// 分页大小（默认为10）
        /// </summary>
        public int PageSize { get; set; } = 10;
    }