private void button_Click(object sender, RoutedEventArgs e)
{
Enums.Discipline myDiscipline;
Enum.TryParse(comboBoxDiscpline.Text, out myDiscipline);
Speciality sp = new Speciality(myDiscipline, tBname.Text, Convert.ToInt32(tBminRate.Text), Convert.ToInt32(tBmaxRate.Text));
bl.addSpec(sp);
_SpecialityCollection.Add(sp);
}