private void AddNewStudent(int rowNumber)
 {
     dataGridStudents["_StudentID", rowNumber].Value =
         StudentDAL.AddNewStudent(dataGridStudents["_First_name", rowNumber].Value.ToString(),
                                  dataGridStudents["_Last_name", rowNumber].Value.ToString(),
                                  dataGridStudents["_Patronymic", rowNumber].Value.ToString(),
                                  null,
                                  dataGridStudents["_Email", rowNumber].Value.ToString(),
                                  dataGridStudents["_Password", rowNumber].Value.ToString(),
                                  null,
                                  dataGridStudents["_Grade", rowNumber].EditedFormattedValue.ToString()
                                  );
 }