private void group_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (semester.Text != "")
{
disc.SelectedItem = null;
ListInterface a = new ClassList();
disc.ItemsSource = a.GetDisciplineSpec(semester.Text, group.SelectedItem.ToString());
}
a3.Visibility = Visibility.Hidden;
if (semester.Text != "" && type.Text != "" && disc.Text != "" && teacher.Text != "")
{
p.Visibility = Visibility.Hidden;
}
}