Listコレクションは、あるフィールドに基づいて再集計される(groupby)

 foreach (var iorder in iOrderList)
                    {
                        var tempIOrderDetailList = iOrderDetailList.Where(v => v.prId == iorder.prId).ToList();//       iOrderDetailList
                        var ix_GoodsIds = (from i in tempIOrderDetailList
                                           group i by i.donvvGoodsId into d
                                           where d.Count() > 1
                                           select d.FirstOrDefault().donvvGoodsId).ToList();//   GoodsId
                        var tempOrderDetailList = (from i in tempIOrderDetailList
                                                   group i by i.donvvGoodsId into d
                                                   where d.Count() > 1
                                                   select new IOrderDetails()
                                                   {
                                                       Id=d.FirstOrDefault().Id,
                                                       prId = d.FirstOrDefault().prId,
                                                       prDetailId = d.FirstOrDefault().prDetailId,
                                                       commodityId = d.FirstOrDefault().commodityId,
                                                       skuId = d.FirstOrDefault().skuId,
                                                       BuyAmt = d.Sum(p => p.BuyAmt),
                                                       skuOrginPrice = d.FirstOrDefault().skuOrginPrice,
                                                       totelAmt = d.Sum(p => p.totelAmt),
                                                       status = d.FirstOrDefault().status,
                                                       erpId = d.FirstOrDefault().erpId,
                                                       donvvGoodsId = d.FirstOrDefault().donvvGoodsId,
                                                       SgccErpOrderDetailId=d.FirstOrDefault().SgccErpOrderDetailId,
                                                       ExpectedArrivalTime=d.FirstOrDefault().ExpectedArrivalTime
                                                   }).ToList();//  

                        var tempOrderDetails = new List();
                        foreach (var ix_GodosId in ix_GoodsIds)
                        {
                            foreach (var iOrderDetail in tempIOrderDetailList)
                            {
                                if (iOrderDetail.donvvGoodsId == ix_GodosId)
                                {
                                    tempOrderDetails.Add(iOrderDetail);
                                }
                            }
                        }
                        iOrderDetailList.RemoveAll(i => tempOrderDetails.Contains(i));//  (    )
                        iOrderDetailList.AddRange(tempOrderDetailList);//        
                    }