void AddOrUpdateTeacher(EncyclopediaContext context, string TrackName, string TeacherName)
{
var crs = context.Tracks.SingleOrDefault(c => c.TrackName == TrackName);
var inst = crs.Teachers.SingleOrDefault(i => i.LastName == TeacherName);
if (inst == null)
{
crs.Teachers.Add(context.Teachers.Single(i => i.LastName == TeacherName));
}
}