private void btn_login_Click(object sender, EventArgs e) { string userName = tb_username.Text.Trim(); string password = tb_pass.Text.Trim(); taiKhoanForm = userName; bool bl = ub.CheckLogin(userName, password); Admin fm = new Admin(); if (bl) { tb_username.Clear(); tb_pass.Clear(); this.Hide(); fm.ShowDialog(); this.Show(); } else { tb_username.Clear(); tb_pass.Clear(); MessageBox.Show("Tai Khoan hoac Mat Khau sai vui long nhap lai!"); } }