private bool IsTimeslotFree(StretchPassing link) {
if (_passings.Where(p =>
(link.Departure >= p.Departure && link.Departure < p.Arrival) ||
(link.Arrival > p.Departure && link.Arrival <= p.Arrival)).Count() > TracksCount)
return false;
return true;
}
internal void Add(StretchPassing link) {
if (link == null) throw new ArgumentNullException(nameof(link));
if (!IsTimeslotFree(link)) {
throw new TimetableException("Timeslot not free."); }
link.TrackLink = this;
_passings.Add(link);
}