private void Button_Click(object sender, RoutedEventArgs e) { if (name.Text == "") { a1.Visibility = Visibility.Visible; p.Visibility = Visibility.Visible; if (hours.Text == "") { a2.Visibility = Visibility.Visible; } if (semester.Text == "") { a3.Visibility = Visibility.Visible; } if (speciality.Text == "") { a4.Visibility = Visibility.Visible; } } else { if (hours.Text == "") { a2.Visibility = Visibility.Visible; p.Visibility = Visibility.Visible; if (semester.Text == "") { a3.Visibility = Visibility.Visible; } if (speciality.Text == "") { a4.Visibility = Visibility.Visible; } } else { if (semester.Text == "") { a3.Visibility = Visibility.Visible; p.Visibility = Visibility.Visible; if (speciality.Text == "") { a4.Visibility = Visibility.Visible; } } else { if (speciality.Text == "") { a4.Visibility = Visibility.Visible; p.Visibility = Visibility.Visible; } else { ListInterface a = new ClassList(); a.AddDiscipline(name.Text, hours.Text, semester.Text, speciality.Text); name.Clear(); hours.Clear(); semester.SelectedIndex = -1; speciality.SelectedIndex = -1; } } } } }