Inner join and outer join options in Entity Framework 4.0

Question

I am using EF 4.0 and I need to implement query with one inner join and with N outer joins I started to implement this using different approaches but get into trouble at some point.

Here is two examples how I started of doing this using ObjectQuery<'T'> and Linq to Entity

1)Using ObjectQuery<'T'> I implement flexible outer join but I don't know how to perform inner join with entity Rules in that case (by default Include("Rules") doing outer join, but i need to inner join by Id).

    public static IEnumerable<Race> GetRace(List<string> includes, DateTime date)
    {
        IRepository repository = new Repository(new BEntities());

        ObjectQuery<Race> result = (ObjectQuery<Race>)repository.AsQueryable<Race>();

        //perform outer joins with related entities
        if (includes != null)                   
            foreach (string include in includes)
                result = result.Include(include);


        //here i need inner join insteard of default outer join
        result = result.Include("Rules"); 

        return result.ToList();
    }

2)Using Linq To Entity I need to have kind of outer join(somethin like in GetRace()) where i may pass a List with entities to include) and also i need to perform correct inner join with entity Rules

    public static IEnumerable<Race> GetRace2(List<string> includes, DateTime date)
    {
        IRepository repository = new Repository(new BEntities());

        IEnumerable<Race> result = from o in repository.AsQueryable<Race>()
                                   from b in o.RaceBetRules
                                   select new
                                   {
                                     o
                                   });

        //I need here:
        // 1. to perform the same way inner joins with related entities like with ObjectQuery above

        //here i getting List<AnonymousType> which i cant cast to 
        //IEnumerable<Race> when i did try to cast like 
        //(IEnumerable<Race>)result.ToList(); i did get error:
        //Unable to cast object of type 
        //'System.Collections.Generic.List`1[<>f__AnonymousType0`1[BetsTipster.Entity.Tip.Types.Race]]' 
        //to type 
        //'System.Collections.Generic.IEnumerable`1[BetsTipster.Entity.Tip.Types.Race]'.
        return result.ToList();
    }

May be someone have some ideas about that.

Answer 1

Here is a post dealing with Inner Join in LINQ to Entities.
Hope this will point the right direction to you.