Question

Still pretty new to entity framework. So forgive me if this is a noob question. Hoping someone can shed some light on this.

I am trying to select data from 3 related tables.

Leagues -> Teams -> Rosters -> 

The relationships are League.LeagueID => Team.LeagueID => Roster.TeamID

In the Roster table there is a PlayerID column

I need a query that can select all leagues where Roster has PlayerID = 1

I cannot seem to filter results on the grandchild record no matter what I try. Not finding too much on the internet either.

I have found a way to do this with anonymous types but those are read only so i can make changes to the data. I must be able to update the data after it returns.

Answer 1

db.Leagues.Where(l => l.Teams.Any(t => t.Roster.PlayerID == 1));

The SQL generated should get you what you want, even it looks unreadable 😉

If you want to specifically use inner joins to do this, you can do so with code like this:

from l in db.Leagues
join t in db.Teams on l.LeagueID equals t.LeagueID
join r in db.Rosters on t.TeamID equals r.TeamID
where r.PlayerID = 1
select l

UPDATE

To do with with eager loading the child associations use Include():

((from l in db.Leagues
join t in db.Teams on l.LeagueID equals t.LeagueID
join r in db.Rosters on t.TeamID equals r.TeamID
where r.PlayerID = 1
select l) as ObjectQuery<League>).Include(l => l.Teams.Select(t => t.Rosters))