Linq中的group by多表多字段，Sum求和

Posted 2020-09-08 szsunny

 var data = (from a in Items
             group a by new { a.GroupId, a.Id } into b
             orderby new ComparerItem() { GroupId = b.Key.GroupId, Id = b.Key.Id } descending
             select new
              {
                 GroupId = b.Key.GroupId,
                 Id = b.Key.Id,
                 Count = b.Sum(c => c.Count),
                 Weight = b.Sum(c => c.Weight)
               }).OrderBy(t => t.GroupId).ThenBy(t => t.Id);

items 是一个包含4个字段(GroupId, Id, Count, Weight)的list.

效果，按GroupId,Id 分组 ，并统计Count字段和Weight字段