private void Add_T()
        {
            StudentDBEntities db      = new StudentDBEntities();
            ThemeDB           dnevnik = new ThemeDB()
            {
                Theme   = Theme_Add,
                Data    = Date_Add,
                Zadanie = Zadanie_Add
            };

            db.ThemeDBs.Add(dnevnik);
            db.SaveChanges();
        }
 private void dataTheme_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     if (this.dataTheme.SelectedIndex >= 0)
     {
         if (this.dataTheme.SelectedItems.Count >= 0)
         {
             if (this.dataTheme.SelectedItems[0].GetType() == typeof(ThemeDB))
             {
                 ThemeDB Edit_S = (ThemeDB)this.dataTheme.SelectedItems[0];
                 Theme_Add_Box.Text   = Edit_S.Theme;
                 Data_Picker.Text     = Edit_S.Data;
                 Zadanie_Add_Box.Text = Edit_S.Zadanie;
                 updatingDnevnikID    = Edit_S.Id;
             }
         }
     }
 }