public GradeListItem(Grade grade)
 {
     GradeID = grade.GradeID;
     Nom = grade.Nom;
     Abreviation = grade.Abreviation;
     Ordre = grade.Ordre;
 }
        public Grade GradeAdd(GradeListItem gradeModel)
        {
            Grade grade = new Grade();
            grade.Nom = gradeModel.Nom;
            grade.Abreviation = gradeModel.Abreviation;
            grade.GradeID = data.GetNextGradeID();

            data.Grades.Add(grade);

            return grade;
        }