c# - Linq to Entities Left outer join分组到一个集合中

Question

from component in Materials.OfType<Container>().Where(m => m.Active)
join segmentFinanceRating in segmentFinanceRatingView on component.Id equals segmentFinanceRating.MaterialId into segmentFinanceRatingGroup
from segmentFinanceRatingWithDefault in segmentFinanceRatingGroup.DefaultIfEmpty()
select new
{
   id = component.Id,
   name = component.Name,
   subType = component.SubType,
   size = component.Size,
   MaterialIds = component.Materials.Select(x => x.Id),
   BrandNames = component.Brands.Select(x => x.Name),
   SegmentRatings = segmentFinanceRatingWithDefault
}

我有上面的 LINQ to Entities 查询，它有一个 LEFT JOIN 来获取给定组件的 1 个或多个段的评级值。

segmentFinanceRating 实体具有属性，{ MaterialId, SegmentId, Rating, LowRated }

目前结果没有分组到相关组件，即 SegmentRatings 属性不是 segmentFinanceRating 对象的单个集合，而是我有多个数据行每个中有 1 个 segmentFinanceRating 对象。

我看过一些使用 group x by y into z 的例子，但我无法让它工作，可能是因为我也需要组件上的一些集合，我是不确定。

如有任何帮助，我们将不胜感激，谢谢。

Answer 1

List 中的 GroupBy 不适合你？

var list = (from component in Materials.OfType<Container>().Where(m => m.Active)
join segmentFinanceRating in segmentFinanceRatingView on component.Id equals segmentFinanceRating.MaterialId into segmentFinanceRatingGroup
from segmentFinanceRatingWithDefault in segmentFinanceRatingGroup.DefaultIfEmpty()
select new
{
   id = component.Id,
   name = component.Name,
   subType = component.SubType,
   size = component.Size,
   MaterialIds = component.Materials.Select(x => x.Id),
   BrandNames = component.Brands.Select(x => x.Name),
   SegmentRatings = segmentFinanceRatingWithDefault
}).ToList().GroupBy(s=> s.SegmentRatings);