private void btnDodaj_Click(object sender, EventArgs e)
 {
     try
     {
         int     ocjena = int.Parse(cmbOcjena.SelectedItem.ToString());
         Predmet p      = cmbPredmeti.SelectedItem as Predmet;
         string  datum  = dateTimePolaganje.Value.ToShortDateString();
         if (!s.JelPolozen(p))
         {
             StudentPredmet sp = new StudentPredmet();
             sp.Ocjena  = ocjena;
             sp.Datum   = datum;
             sp.Predmet = p;
             s.Uspjeh.Add(sp);
             DLWMS.Bazza.SaveChanges();
             MessageBox.Show("Uspjesno dodan.");
             chbPolozeni.Checked = false;
             UcitajPolozene();
         }
         else
         {
             MessageBox.Show("Vec polozen.");
         }
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message + ex.InnerException?.Message);
     }
 }
 void Dodaj100Predmeta(Predmet p, int ocj, string datum)
 {
     for (int i = 0; i < 500; i++)
     {
         StudentPredmet sp = new StudentPredmet();
         sp.Predmet = p;
         sp.Ocjena  = ocj;
         sp.Datum   = datum;
         s.Uspjeh.Add(sp);
     }
     DLWMS.Bazza.SaveChanges();
 }