private void btnLogin_Click(object sender, EventArgs e)
        {
            tbl_TaiKhoan account = db.tbl_TaiKhoans.FirstOrDefault(res => res.TenDangNhap.Equals(tbUsername.Text) && res.MatKhau.Equals(tbPassword.Text));

            if (account != null)
            {
                SessionInfo.username      = account.TenDangNhap;
                SessionInfo.authorization = account.Quyen;
                FrmMain frm = new FrmMain();
                this.Hide();
                frm.ShowDialog();
                this.Show();
                tbPassword.Clear();
            }
            else
            {
                DevExpress.XtraEditors.XtraMessageBox.Show("Sai thông tin đăng nhập!", "Lỗi");
            }
        }
 partial void Updatetbl_TaiKhoan(tbl_TaiKhoan instance);
 partial void Deletetbl_TaiKhoan(tbl_TaiKhoan instance);
 partial void Inserttbl_TaiKhoan(tbl_TaiKhoan instance);