如何从ASP.NET MVC中的自定义帮助器方法中访问当前的System.Web.Routing.RequestContext？

public static string GetCurrentRouteData(this HtmlHelper helper)
{
    var requestContext = HttpContext.Current.Request.RequestContext;
    var routeData = requestContext.RouteData;
    var controller = routeData.Values["controller"].ToString();
    var action = routeData.Values["action"].ToString();

    return $"Controller: {controller}, Action: {action}";
}

public static string GetRouteData(this HtmlHelper helper, RequestContext requestContext)
{
    var routeData = requestContext.RouteData;
    var controller = routeData.Values["controller"].ToString();
    var action = routeData.Values["action"].ToString();

    return $"Controller: {controller}, Action: {action}";
}