public void AddCalification(string courseName, int studentId, int calification)
{
lock (Inscriptions)
{
StudentCourse inscription = Inscriptions.Find(i => i.CourseName == courseName && i.StudentId == studentId);
if (inscription == null)
{
throw new CourseException("Student it's not enrolled in the course");
}
inscription.AddCalification(calification);
}
}