private void CbxDepartments_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
{
var selectedDepartmentId = DepartmentId;
ObservableCollection <StudyProgram> SP = new ObservableCollection <StudyProgram>(ServiceDataProvider.GetAllSPForDepartmentId(selectedDepartmentId));
if (SP.Count == 0)
{
e.Handled = true;
}
view.cbxStudyPrograms.ItemsSource = SP;
}