Question

I use Entity Framework and have this entity mapping:

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

I want a Linq query similar to this (but one that will work 🙂

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

It should return the following (only the active records):

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

Answer 1

If you want parents with at least one active child:

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

If you want parents with all active children:

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

If you wanted to filter the children as part of the same query you could do something like:

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

Or

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) }