EFCore 多字段排序分页法

模型:

 public class IPageCommand
    {
        public string Keyword { get; set; }
        public int PageIndex { get; set; }
        public int PageSize { get; set; }
        public OrderModelField[] OrderModelField { get; set; }
    }
    public struct OrderModelField
    {
        public string SortField { get; set; }
        public bool IsDesc { get; set; }
    }

方法:

/// <summary>
        /// 根据条件获取多个实体
        /// </summary>
        /// <param name="where"></param>
        /// <returns></returns>
        public List<TResult> GetPageList<TEntity, TResult>(Expression<Func<TEntity, TResult>> select, Expression<Func<TEntity, bool>> where, int pageIndex, int pageSize, out long total, params OrderModelField[] orderByExpression)
            where TEntity : class
        {
            //条件过滤
            var query = _context.Set<TEntity>().Where(where);

            //创建表达式变量参数
            var parameter = Expression.Parameter(typeof(TEntity), "o");

            if (orderByExpression != null && orderByExpression.Length > 0)
            {
                for (int i = 0; i < orderByExpression.Length; i++)
                {
                    //根据属性名获取属性
                    var property = typeof(TEntity).GetProperty(orderByExpression[i].SortField);
                    //创建一个访问属性的表达式
                    var propertyAccess = Expression.MakeMemberAccess(parameter, property);
                    var orderByExp = Expression.Lambda(propertyAccess, parameter);

                    string OrderName = "";
                    if (i > 0)
                        OrderName = orderByExpression[i].IsDesc ? "ThenByDescending" : "ThenBy";
                    else
                        OrderName = orderByExpression[i].IsDesc ? "OrderByDescending" : "OrderBy";


                    MethodCallExpression resultExp = Expression.Call(typeof(Queryable), OrderName, new Type[] { typeof(TEntity), property.PropertyType }, query.Expression, Expression.Quote(orderByExp));

                    query = query.Provider.CreateQuery<TEntity>(resultExp);
                }
            }

            total = query.Count();
            return query.Skip((pageIndex - 1) * pageSize).Take(pageSize).Select(select).ToList();
        }

参数:

{ 
 "Keyword": "string",
  "PageIndex": 2,
  "PageSize": 5,
  "OrderModelField": [
    {
      "SortField": "CreateTime",
      "IsDesc": true},
{
      "SortField": "String",
      "IsDesc": true}

  ]
}

 调用:

 public List<ExampleResult> GetList(PagedCommand Cmd, long total)
        {
            
            return GetPageList<ExampleEntity, ExampleResult>(x => new ExampleResult
            {
                Id = x.Id,
                Boolean = x.Boolean,
                CreateTime = x.CreateTime,
                Decimal = x.Decimal,
                Enum = x.Enum,
                Float = x.Float,
                Int = x.Int,
                String = x.String
            }, x => x.Boolean, Cmd.PageIndex, Cmd.PageSize, out total, Cmd.OrderModelField);

        }

 

posted @ 2018-02-04 21:45  码农丁  阅读(1794)  评论(0编辑  收藏  举报