Add a stylesheet from custom DNN module settings

HtmlGenericControl css1 = new HtmlGenericControl("link");
css1.Attributes["type"] = "text/css";
if (Settings.Contains("jQueryUI"))
{
 css1.Attributes["href"] = Settings["jQueryUI"].ToString();
}
else
{
 css1.Attributes["href"] = "https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.1/themes/redmond/jquery-ui.css";
}
css1.Attributes["rel"] = "stylesheet";
css1.Attributes["media"] = "screen";
Page.Header.Controls.Add(css1);