Going deeper: ThenInclude / ThenPreload

ThenInclude and ThenPreload load the next level, from the nodes the previous Include loaded. When that Include names a relation end, give it the related node type, so the next level knows what it starts from:

var venues = db.Query<IVenue>()
               .Include<IEvent>(v => v.Events)             // venue → its events
               .ThenInclude(e => e.Attendees, top: 20)     // event → its attendees
               .Execute();

ThenPreload does the same for references: .Include<IEvent>(v => v.Events).ThenPreload(e => e.Cover).