聚合统计时 group by 的字段格式化怎么处理？

[zhza]

比如需要 topic 表 addtime 为 datetime 类型
需要 select date( addtime ) , count(1) from topic group by date(addtime);

fslq.Select().GroupBy( a=> ?????? ) .ToList(a=>new { key = a.Key,Size = a.Count() } );

[2881099]

fslq.Select().GroupBy( a=> a.addtime.Date ) .ToList(a=>new { key = a.Key,Size = a.Count() } );