private void MenuItemObrisi_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                if (radioButton_searchKlijenta.IsChecked == true)
                {
                    KlijentDAO k1 = new KlijentDAO("localhost", "Centar", "root", "");
                    Klijent k = new Klijent();
                    k = listBox_login.SelectedItem as Klijent;
                    k1.delete(k);

                }
                else if (radioButton_searchPsa.IsChecked == true)
                {
                    PasDAO pas1 = new PasDAO("localhost", "Centar", "root", "");
                    Pas p = new Pas();
                    p = listBox_login.SelectedItem as Pas;
                    pas1.delete(p);

                }
                else if (radioButton_searchRadnika.IsChecked == true)
                {
                    RadnikDAO radnik1 = new RadnikDAO("localhost", "Centar", "root", "");
                    Radnik r = new Radnik();
                    r = listBox_login.SelectedItem as Radnik;
                    radnik1.delete(r);
                }
                listBox_login.Items.Remove(listBox_login.SelectedItem);
            }
            catch (Exception izuz)
            {
                System.Windows.Forms.MessageBox.Show(izuz.Message);
            }
        }