private void GetData()
        {
            StudentBll studentBll = new StudentBll();

            list = studentBll.GetAnnouncements();
            AnnouncementComboBox.DataContext = list;
            for (int i = 0; i < list.Count; i++)
            {
                ComboBoxItem item = new ComboBoxItem();
                item.Content = list[i].Title;
                AnnouncementComboBox.Items.Add(item);
            }
        }