private void RequiringExemptionExamSelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (RequiringExemptionExams.SelectedValue != null)
{
Exam ex = (Exam)RequiringExemptionExams.SelectedValue;
Student st = (Student)RequiringExemption.SelectedValue;
PreviousAttempts.ItemsSource = ex.AttemptsBy((Student)RequiringExemption.SelectedValue);
RequiringGiveExemptionButton.IsEnabled = st.CanGetExemption(ex);
}
else
{
PreviousAttempts.ItemsSource = null;
RequiringGiveExemptionButton.IsEnabled = false;
}
}