public static void addPlan(CPlanEntity planData)
 {
     dbContext        = new StudentPlanManagementData.StudentPlanManagementContext();
     planData.Student = dbContext.StudentEntities.SingleOrDefault(s => s.StudentId == planData.Student.StudentId); //TODO tai sao loi da them o truoc ma
     dbContext.PlanEnties.Add(planData);
     dbContext.SaveChanges();
 }
        public static void addMarkNew(CMarksEntity mark, string strStudentId, string strSemesterId, string strSubjectId)
        {
            dbContext = new StudentPlanManagementData.StudentPlanManagementContext();
            mark.Take = dbContext.SubjectsTakesEntities.SingleOrDefault(t => t.StudentId == strStudentId && t.SemesterId == strSemesterId && t.SubjectId == strSubjectId);

            dbContext.MarkEnties.Add(mark);
            dbContext.SaveChanges();
        }