private void btnAzurirajSmer_Click(object sender, EventArgs e)
        {
            if (Provera.proveraSmera(txtboxIDSmera.Text, txtboxNazivSmera.Text, txtboxIDSkole2.Text))
            {
                //  1
                int    idSmera    = int.Parse(txtboxIDSmera.Text);
                string nazivSmera = txtboxNazivSmera.Text;
                int    idSkole    = int.Parse(txtboxIDSkole2.Text);

                //  2
                bool success = databaseHelper.UpdateDataInSmer(idSmera, nazivSmera, idSkole);
                if (success == true)
                {
                    MessageBox.Show("Smer je uspešno ažuriran.");

                    DataTable dt = databaseHelper.SelectDataFromSmer();
                    dataGridViewSmer.DataSource = dt;

                    Clear();
                }
                else
                {
                    MessageBox.Show("Greška prilikom ažuriranja smera! Pokušaj opet.");
                }
            }
        }
        private void btnObrisiSmer_Click(object sender, EventArgs e)
        {
            if (Provera.proveraSmera(txtboxIDSmera.Text, "pr", "123"))
            {
                //  1
                int idSmera = int.Parse(txtboxIDSmera.Text);

                //  2
                bool success = databaseHelper.DeleteDataInSmer(idSmera);
                if (success == true)
                {
                    MessageBox.Show("Smer je uspešno obrisan.");

                    DataTable dt = databaseHelper.SelectDataFromSmer();
                    dataGridViewSmer.DataSource = dt;

                    Clear();
                }
                else
                {
                    MessageBox.Show("Greška prilikom brisanja smera! Pokušaj opet.");
                }
            }
        }