delegate bool ShowSoftwareKeyboardCallback(IntPtr focusedElement);
private static ShowSoftwareKeyboardCallback _showSoftwareKeyboard = ShowSoftwareKeyboard;
[MonoPInvokeCallback(typeof(ShowSoftwareKeyboardCallback))]
private static bool ShowSoftwareKeyboard(IntPtr focusedElement)
{
    try
    {
        if (_initialized)
        {
            UIElement element = Extend.GetProxy(focusedElement, false) as UIElement;
            return _softwareKeyboard.Show(element);
        }
    }
    catch (Exception e)
    {
        Noesis.Error.SetNativePendingError(e);
    }

    return false;
}