private void FormStudent_FormClosing(object sender, FormClosingEventArgs e)
 {
     if (countEdit != 0)
     {
         parentManager.CheckCorrectStudentData();
         parentManager.UpdateState();
     }
     managerStudent.Close();
 }
 private void FormDiscipline_FormClosing(object sender, FormClosingEventArgs e)
 {
     if (countEdit != 0)
     {
         parentManager.CheckCorrectDisciplineData();
         parentManager.UpdateState();
     }
     managerDiscipline.Close();
 }