protected void Page_Load(object sender, EventArgs e) { if (IsPostBack) { Session["DN"] = null; bool check = xl.CheckDangNhap(txtTaiKhoan.Text.Trim(), txtMatKhau.Text.Trim()); if(check==true) { Session["DN"] = txtTaiKhoan.Text; Response.Redirect("GioiThieu.aspx", false); } } }