public static void init_Students()
        { //מילוי המערך מתוך בסיס הנתונים
            SqlCommand c = new SqlCommand();

            c.CommandText = "EXECUTE dbo.Get_All_Students";
            SQL_CON       SC  = new SQL_CON();
            SqlDataReader rdr = SC.execute_query(c);

            students = new List <Student>();

            while (rdr.Read())
            {
                Classes cl = (Classes)Enum.Parse(typeof(Classes), rdr.GetValue(10).ToString());
                Student s  = new Student(rdr.GetValue(0).ToString(), rdr.GetValue(1).ToString(), rdr.GetValue(2).ToString(), rdr.GetValue(3).ToString(), DateTime.Parse((rdr.GetValue(4).ToString())),
                                         rdr.GetValue(5).ToString(), rdr.GetValue(6).ToString(), rdr.GetValue(7).ToString(), rdr.GetValue(8).ToString(), rdr.GetValue(9).ToString(), cl, int.Parse(rdr.GetValue(11).ToString()), rdr.GetValue(13).ToString());
                students.Add(s);
                foreach (StudentGroup sg in studentGroups)
                {
                    if (sg.getId().ToString() == rdr.GetValue(12).ToString())
                    {
                        s.setStudentGroup(sg);
                        sg.addStudent(s);
                    }
                }
            }
        }