ErrorProvider in an User control in C#

Question

I have an UserControl CambioContraseña with two textBox of other customized UserControl called txtAlfanumerico. This UserContol is very simple but I want to add an ErrorProvider to check the fields are not empty. This is a screen capture of UserControl:

And this is an code:

public bool FaltaCampos() {
  bool falta = false;
  foreach(txtAlfanumerico txt in Controls.OfType < txtAlfanumerico > ()) {
    if (txt.Text == "") {
      errorProviderFalta.SetError(txt, "Falta " + txt.Tag.ToString());
      falta = true;
    } else {
      errorProviderFalta.SetError(txt, "");
    }
  }
  return falta;
}

And the code in where I use this UserControl:

private void buttonConfirmar_Click(object sender, EventArgs e) {
  try {
    if (!cambioContraseña1.FaltaCampos()) {
      string actual = cambioContraseña1.TextBoxContraseñaActual();
      string nueva = cambioContraseña1.TextBoxNuevaContraseña();
      persona.CambiarContraseña(actual, nueva);
    }
  } catch (Exception ex) {
    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
  }
}

But my problem is that ErrorProvider do not work in the Form that I use, icons do not appear directly.

I did a breakpoint into FaltaCampos and these are results:

Answer 1

I can to resolve my problem I think that I had not compiled the UserControl when I did the changes, so the ErrorProvider didn't appear.