Keyboard won't dismiss even after Focus change

Question

I am creating a Windows 8.1 app and after the user presses a button, a popup opens over most of the screen. There are several textboxes inside the popover.

I found

Answer 1

In my app this works fine:

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    this.KeyDown += Strona_KeyDown;
}

private void Strona_KeyDown(object sender, KeyRoutedEventArgs e)
{
    if (e.Key == Windows.System.VirtualKey.Enter)
    {
        this.Focus(FocusState.Pointer);
    }
}