c# - 内部列表上的 Entity Framework 过滤器

Question

我使用 Entity Framework 并具有此实体映射:

Parent
- Child 1 (ActiveInd = "Y")
- Child 2 (ActiveInd = "N")
- Child 3 (ActiveInd = "Y")

我想要一个与此类似的 Linq 查询(但可以工作:)

Parent parent = (from p in DataContext.Current.Parents 
where p.ParentId == _parentId 
&& p.Children.Active == true select p).FirstOrDefault();

它应该返回以下内容(仅事件记录):

Parent
- Child 1 (ActiveInd = "Y")
- Child 3 (ActiveInd = "Y")

Answer 1

如果您希望 parent 有至少一个活跃的 child :

from p in DataContext.Current.Parents
where p.ParentId == _parentId && p.Children.Any(c => c.Active)
select p

如果您希望 parent 拥有所有活跃的 child :

from p in DataContext.Current.Parents
where p.ParentId == _parentId && p.Children.All(c => c.Active)
select p

如果你想在同一个查询中过滤 child ，你可以这样做:

from p in DataContext.Current.Parents
where p.ParentId == _parentId 
select new { Parent = p, ActiveChildren = p.Children.Where(c => c.Active) } into parentWithActiveChildren
where parentWithActiveChildren.FilteredChildren.Any()
select parentWithActiveChildren

或者

from p in DataContext.Current.Parents
where p.ParentId == _parentId && p.Children.Any(c => c.Active)
select new { Parent = p, ActiveChildren = p.Children.Where(c => c.Active) }