Question

我有这个查询

var query = from v in this._venueRepository.Table
                        join s in this._storeRepository.Table on v.VenueID equals s.VenueID
                        join w in this._workstationRepository.Table on s.StoreID equals w.StoreID
                        join t in this._tillSummaryRepository.Table on w.WorkstationID equals t.TillOpID
                        group new { v.DiscItemName_1, t.DiscItem_1, t.QDiscItem_1 } by new { v.DiscItemName_1 } into g
                        select new { Discount = g.Key, Amount = g.Sum(p => p.DiscItem_1), Qty = g.Sum(p => p.QDiscItem_1) };

我想执行此查询（可能是异步）但每次执行此查询时我都想更新参数“_1” - ＆gt; “_2” - ＆gt;例如“_3”等

var query = from v in this._venueRepository.Table
                        join s in this._storeRepository.Table on v.VenueID equals s.VenueID
                        join w in this._workstationRepository.Table on s.StoreID equals w.StoreID
                        join t in this._tillSummaryRepository.Table on w.WorkstationID equals t.TillOpID
                        group new { v.DiscItemName_2, t.DiscItem_2, t.QDiscItem_2 } by new { v.DiscItemName_2 } into g
                        select new { Discount = g.Key, Amount = g.Sum(p => p.DiscItem_2), Qty = g.Sum(p => p.QDiscItem_2) };

等等等我有什么想法可以做到这一点？也许反思？

Answer 1

当你提到时，这样做的一种方式当然是反思。基于您的示例的示例如下：

var t = ._venueRepository.Table.FirstOrDefault().GetType();

for(int iterationCount = 1; iterationCount < MAX_ITERATIONS ; iterationCount++)
{

PropertyInfo itemNameProperty = t.GetProperty(String.Format("DiscItemName_{0}", iterationCount));
PropertyInfo discItermProperty = t.GetProperty(String.Format("DiscItem_{0}", iterationCount));
//Repeat the above for all properties.

var query = from v in this._venueRepository.Table
                    join s in this._storeRepository.Table on v.VenueID equals s.VenueID
                    join w in this._workstationRepository.Table on s.StoreID equals w.StoreID
                    join t in this._tillSummaryRepository.Table on w.WorkstationID equals t.TillOpID
                            //Repeat the below for other properties
                    group new { itemNameProperty.GetValue(v), dicItemProperty.GetValue(v) , qDiscProperty.GetValue(v) } by new { itemNameProperty.GetValue(v) } into g
                    //Similarly do for the select new.
                    select new { Discount = g.Key, Amount = g.Sum(p => p.DiscItem_1), Qty = g.Sum(p => p.QDiscItem_1) };

//Other code here.
}

如果您使用的是Entity框架，则上述查询将无效。这不起作用的原因是实体框架将尝试将您的查询转换为SQL，并且将在反射部分失败。您需要做的是将查询分成两部分。进行过滤并一步完成并将其检索到List，然后使用反射在另一个查询中创建匿名类型。但是，对于此操作，您将使用更多内存，并且您正在失去使用Linq to Entity的好处。

通过更新属性名称循环linq查询n次

1 个答案: