protected void btn_Click(object sender, EventArgs e) { try { String pass = EncodePassword(password.Text); Connect_SQL sql = new Connect_SQL(); var param = new List <Tuple <string, string> >(); param.Add(Tuple.Create("@name", user.Text)); param.Add(Tuple.Create("@pass", pass)); String query = "select_Account"; if (sql.Get_Data(query, param).Rows.Count > 0) { Session["login"] = 1; Response.Redirect("Form_Main.aspx"); } else { Session["login"] = null; lblCheck.Text = "Incorrect username or password"; } } catch (NullReferenceException) { lblCheck.Text = "Connect to Database fail"; } }