private void button1_Click(object sender, EventArgs e) { string allowedchar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; if (textBox1.Text == "" || textBox2.Text == "") { MessageBox.Show("You must fill in all fields"); } else if (!textBox2.Text.All(allowedchar.Contains)) { MessageBox.Show("Check the password"); } else { korisnik k = new korisnik(); k.korisnickoIme = textBox1.Text; k.sifra = textBox2.Text; DataTable dt = Base.Login(k); try { if (k.proveraKorisnika()) { if (dt.Rows.Count == 1) { switch (dt.Rows[0][5] as string) { case "A": { k.korisnickoIme = dt.Rows[0][4].ToString(); this.Hide(); Admin a = new Admin(); a.Show(); break; } case "R": { k.korisnickoIme = dt.Rows[0][4].ToString(); User u = new User(); u.Show(); break; } default: { MessageBox.Show("You entered your username or password incorrectly."); break; } } } else { MessageBox.Show("You entered your username or password incorrectly."); } } else { MessageBox.Show("There is no user with the username entered."); } } catch (Exception ex) { MessageBox.Show(ex.Message); } } }