private void btnZimmetCikar_Click(object sender, EventArgs e)
        {
            if ((string.IsNullOrEmpty(cmbCikarilanKullaniciAdi.Text)) || (string.IsNullOrEmpty(cmbCikarilanAd.Text)) || (string.IsNullOrEmpty(cmbCikarilanMarka.Text)) || (string.IsNullOrEmpty(cmbCikarilanModel.Text)))
            {
                MessageBox.Show("Alanlar boş geçilemez.");
                return;
            }

            ZimmetController.ZimmetKaldir(db, cmbCikarilanKullaniciAdi.SelectedItem.ToString(), cmbCikarilanAd.SelectedItem.ToString(), cmbCikarilanMarka.SelectedItem.ToString(), cmbCikarilanModel.SelectedItem.ToString());
            string secilen = cmbCikarilanAd.SelectedItem.ToString();

            cmbCikarilanAd.Items.Clear();
            cmbCikarilanMarka.Items.Clear();
            cmbCikarilanModel.Items.Clear();
            db.SaveChanges();
        }
        private void btnZimmetle_Click(object sender, EventArgs e)
        {
            if ((string.IsNullOrEmpty(cmbKullaniciAdi.Text)) || (string.IsNullOrEmpty(cmbUrunAd.Text)) || (string.IsNullOrEmpty(cmbMarka.Text)) || (string.IsNullOrEmpty(cmbModel.Text)))
            {
                MessageBox.Show("Alanlar boş geçilemez.");
                return;
            }

            ZimmetController.Zimmetle(db, cmbKullaniciAdi.SelectedItem.ToString(), cmbUrunAd.SelectedItem.ToString(), cmbMarka.SelectedItem.ToString(), cmbModel.SelectedItem.ToString());
            cmbUrunAd.Items.Clear();
            foreach (Esya es in db.Esya)
            {
                foreach (Depo d in db.Depo)
                {
                    if ((es.EsyaId == d.EsyaId) && (d.StokMiktari > 0) && !(cmbUrunAd.Items.Contains(es.EsyaAdı)))
                    {
                        cmbUrunAd.Items.Add(es.EsyaAdı);
                    }
                }
            }
            cmbMarka.Items.Clear();
            cmbModel.Items.Clear();
        }