public Course CreateCourse(Member professor, int periodTime, DateTime?beginning, int maxParticipants, string location, string range)
{
var course = Courses.Create();
course.PeriodTime = periodTime;
course.Beginning = beginning;
course.MaxParticipants = maxParticipants;
course.Location = location;
course.RangeOfAge = range;
// ici on établit les relations dans le sens N-1
course.Professor = professor;
course.ProfessorPseudo = professor.Pseudo;
Courses.Add(course);
return(course);
}