private void button1_Click(object sender, EventArgs e) { SqlConnection conn = new SqlConnection(@"Data Source=DESKTOP-C339597\COUNDOULT;Initial Catalog=Gestioncommerciale;Integrated Security=True"); SqlDataAdapter sda = new SqlDataAdapter("select count(*) from Utilisateur where Login = '******' and Password = '******'", conn); DataTable dt = new DataTable(); sda.Fill(dt); if (dt.Rows[0][0].ToString() == "1") { this.Hide(); article mm = new article(); mm.Show(); } else { MessageBox.Show(" please enter correct login and password", "alert", MessageBoxButtons.OK, MessageBoxIcon.Error); } }