asp.net core 3.1 efcore group by 使用

  //获取上下文
                        var recordContext = _dbContext.Set<tenant_couponrecord>();
                        var groupByCoupon = (from r in recordContext
                                             where r.tenant_id == tenant_id && r.shop_code == shop_code && couponIdlist.Contains(r.CouponId)
                                             group r by r.CouponId into gc
                                             select new { CouponId = gc.Key, Count = gc.Count() }).ToList();

                        if (groupByCoupon != null && groupByCoupon.Count > 0)
                        {
                            foreach (var c in ret)
                            {
                                var groupC = groupByCoupon.Find(p => p.CouponId == c.Id);
                                if(groupC!=null)
                                {
                                    c.RecoredCount = groupC.Count;
                                }
                              
                            }
                        }

1、先获取该表/实体的 dbContext上下文；

2、写linq的lambda表达式；

3、表达式外面套一个ToList()，就可以像正常的List正常使用了。