Another Method, in the application PreRequestHandlerExcute
void Application_PreRequestHandlerExecute(object sender, EventArgs e)
{
Page page = Context.Handler as Page; if (page == null) return; //Get the theme 
page.PreInit += delegate
{ page.Theme = theme; //Update the cookie 
};
}不过这个方法还要配合其它代码来一起实现才可以