private void btnLogin_Click(object sender, EventArgs e)
{
if (TaiKhoanData.CheckLogin(txtUsername.Text.Trim().ToString(), txtPassword.Text))
{
lblInvalid.Visible = false;
this.Visible = false;
frmMaintainSpeciality form = new frmMaintainSpeciality();
form.LoginedUser = txtUsername.Text.Trim().ToString();
form.Visible = true;
}
else
{
lblInvalid.Visible = true;
}
}