private void btnDangNhap_Click(object sender, EventArgs e)
        {
            var           tb   = new HideNotifications();
            SqlConnection conn = dl.Connect();
            string        sql  = "select MaND, TenDangNhap,ChucVu from NguoiDung where TenDangNhap = '" + txtTenDangNhap.Text + "' and MatKhau = '" + txtMatKhau.Text + "'";
            DataTable     dt   = NguoiDung.GetDataTable(conn, sql);

            if (txtMatKhau.Text != "" && txtTenDangNhap.Text != "")
            {
                if (dt.Rows.Count > 0)
                {
                    foreach (DataRow dr in dt.Rows)
                    {
                        PhanQuyenNguoiDung.TenDangNhap = dr["TenDangNhap"].ToString();
                        PhanQuyenNguoiDung.ChucVu      = dr["ChucVu"].ToString();
                        frmMain f = new frmMain();
                        f.OnOff(this.ParentForm);
                        this.Close();
                    }
                }
                else
                {
                    txtMatKhau.Clear();
                    txtTenDangNhap.Clear();
                    //TaoChuChim();
                    txtTenDangNhap.Focus();
                    lblThongBao.Text = "Tên tài khoản hoặc mật khẩu không chính xác";

                    tb.stt(lblThongBao);
                }
            }
            else
            {
                txtMatKhau.Clear();
                txtTenDangNhap.Clear();
                //TaoChuChim();
                txtTenDangNhap.Focus();
                lblThongBao.Text = "Vui lòng nhập đầy đủ thông tin!";

                tb.stt(lblThongBao);
            }
        }
 public string Login(string name, string pass)
 {
     if (name != "" && pass != "")
     {
         SqlConnection conn = dl.Connect();
         string        sql  = "select MaND, TenDangNhap,ChucVu from NguoiDung where TenDangNhap = '" + name + "' and MatKhau = '" + pass + "'";
         DataTable     dt   = NguoiDung.GetDataTable(conn, sql);
         if (dt.Rows.Count > 0)
         {
             return("successed");
         }
         else
         {
             return("failed");
         }
     }
     else
     {
         return("failed");
     }
 }