CSS Bundling output file not generating

Question

um using SquishIt to bundle css in a particular folder and my code is as follows

 public class HomeController : Controller
 {
    public ActionResult Index()
    {
        var stsring = Bundle.Css().Add("~/css/A.css").Add("~/css/b.css").Add("~/css/c.css").Render("~/css/AAA.css");


        return View();
    }}

this works without giving any errors or exceptions , but unfortunately No output file can be found . I have no idea the reason behind it , I will be grateful if anyone can do any suggestions