C#中根据集合中的某些元素实现去重功能

例如这是一个集合，我们想把 Adate AStartTimeId AEndTimeId AGroundFieldAId 一样的去重

http://www.cnblogs.com/zhangxiaolei521/p/5234939.html

sql么？
select min(agroundfieldname), min(aid), adate, astarttimeid, aendtimeid, min(atablename), min(atableaid), min(aisuse), agroundfieldaid from table group by adate, astarttimeid, aendtimeid, agroundfieldaid