async await

 public string GetTestString()
        {
            string sReturn = "";
            string[] sList = { "a", "b", "c", "d", "e", "f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z" };
            for (int i=1;i<6;i++)
            {
                Thread.Sleep(1000);
                Random r = new Random();
                int n = r.Next(1, 26);
                sReturn += sList[n];
            }
            return sReturn;
        }

public ActionResult Contact()
        {
            ViewBag.Start = DateTime.Now;

            BookService BookDAL = new BookService();
            string s1 = BookDAL.GetTestString();
            string s2 = BookDAL.GetTestString();
            string s3 = BookDAL.GetTestString();
            string s4 = BookDAL.GetTestString();

            ViewBag.sValue = s1 + "-" + s2 + "-" + s3 + "-" + s4;

            ViewBag.Message = "Your contact page.";

            ViewBag.End = DateTime.Now;
            return View();
        }

   public async Task<ActionResult> About()
        {
            ViewBag.Start = DateTime.Now;

            ViewBag.Message = "Your application description page.";

            BookService BookDAL = new BookService();

            var s1 =  GetStringAsync(BookDAL);
            var s2 =  GetStringAsync(BookDAL);
            var s3 =  GetStringAsync(BookDAL);
            var s4 =  GetStringAsync(BookDAL);

            await Task.WhenAll(s1, s2, s3, s4);
            ViewBag.sValue = s1.Result + "-" + s2.Result + "-" + s3.Result + "-" + s4.Result;
            ViewBag.End = DateTime.Now;

            return View();
        }

        public async Task<string> GetStringAsync(BookService BookDAL)
        {
            return await Task.Run(() =>
            {
                return BookDAL.GetTestString();
            });
        }