How to filter IList subquery EF Core 2.2

Question

I have these (simplified) models:

public class Participant {
    public Guid Id { get; set; }
    public string Name { get; set; }
    public Guid TeamId { get; set; }
    public Team Team { get; set; }
}

public class Team {
    ...
}

public class Activity {
    public Guid Id { get; set; }
    public string Name { get; set; }
    public int Status { get; set; }
    public IList<ActivityAttendee> ActivityAttendees { get; set; }
}

public class ActivityAttendee {
    public Guid Id { get; set; }
    public Guid ActivityId { get; set; }
    public Guid ParticipantId { get; set; }
    public int Status { get; set; }
    public Participant Participant { get; set; }
}

The participant is identified with this:

Guid? participantId = Guid.TryParse(HttpContext.User.Claims.FirstOrDefault(c => c.Type == "Id")?.Value, out Guid tmp) ? (Guid?)tmp : null;

I query the activities like this:

var activities = await _context.Activities.Include(x => x.ActivityAttendees).ThenInclude(x => x.Participant).Where(x => x.Status == 1).AsNoTracking().ToListAsync();

Now I need to filter Activities where the participant attends. I've tried:

var participantActivities = activities.Where(x => x.ActivityAttendees.ParticipantId == participantId);

var participantActivities = activities.Where(x => x.ActivityAttendees.Contains(y => x.ActivityAttendees.Where(z => z.ParticipantId == participantId)));

var participantActivities = activities.Where(x => x.ActivityAttendees.Any(y => y.ParticipantId == participantId))

How can I accomplish that?

In "normal" SQL I would do something like:

SELECT Id, Name FROM Activities WHERE Id IN (Select ActivityId FROM ActivityAttendees WHERE ParticipantId = participantId))

Next, I also need to filter the activities where the participant doesn't attend but where a team member does (grouped by ActivityAttendee.Participant.TeamId), but I think I can do that when the question above is answered.

Answer 1

正确的方法是：

var participantActivities = activities.Where(x => x.ActivityAttendees.Any(y => y.ParticipantId == participantId));