Question

How to select all records from one table that have corespondent keys with other, using joining table. I have table dbo.Patients and dbo.Hospitals and dbo.PatientHospitals which has Primary keys from both tables. I need all recods from dbo.Patients that are in dbo.Hospitals, that is that are in joining table dbo.PatientHospitals, something like:

var currentHospital = db.Hospitals.Single(x => x.User_Id == UserID);

var model = db.Patients.Include("Hospitals")
              .Select(x => x.Hospitals == currentHospital);  

Answer 1

In code first, you do not need additional table for simple many-to-many relationship. You could define your entities like this

public class Patient
{
    ...    
    public virtual ICollection<Hospital> Hospitals { get; set; }    
    ...
}

public class Hospital
{
    ...    
    public virtual ICollection<Patient> Patients { get; set; }    
    ...
}

And then you could just write currentHospital.Patients