private void DeleteSemester(object sender, RoutedEventArgs e) { if (Semesters.SelectedItem == null) { MessageBox.Show("Please select semester"); return; } var result = MessageBox.Show("Are you sure you want delete current semester?\n That action will remove all related data ", "Confirm", MessageBoxButton.YesNo); if (result == MessageBoxResult.No) { return; } var semesterToDelete = Semesters.SelectedItem as Semester; _semesterRepository.DeleteSemester(semesterToDelete); _allSemesters.Remove(semesterToDelete); Semesters.Items.Refresh(); if (_allSemesters.Count > 0) { Semesters.SelectedIndex = 0; return; } OutOfSemestersHandler(); }