Question

I am trying to create a list of aggregate data by site, using linq to entities.

the code first model has a TrialParticipant class which contains a property representing a one to many relationship StudyCentre, and an ICollection of AdverseEvents, representing a many to one relationship.

Amongst other details, I would like to know the count of AdverseEvents per StudyCentre.

The code

var returnVal =
    (from participant in _db.TrialParticipants
     group participant by participant.StudyCentreId into centre
     select new StudyCentreStatistic
     { 
        TotalNo = centre.Count(),
        ...
        AdverseEventNo = centre.Sum(participant=>participant.AdverseEvents.Count)
     }).ToList();

But this creates an error:

There was an error parsing the query. [ Token line number = 72,Token line offset = 4,Token in error = SELECT

Any ideas about how to do this would be much appreciated. Thank you.

Answer 1

If there is a navigation property StudyCentre.Participants you can do:

from s in _db.StudyCentres
select new
{ 
    s.StudyCentreId,
    AdverseEventCount = s.Participants.SelectMany(p => p.AdverseEvents).Count()
}