Transaction based approch in asp.net mvc5

Question

My application is in N tier architechture i just want to make it as transaction based

 

should i add transaction globally

 public ActionResult adddepartment(LbMsDepartment dt)
        {

            dt.CreatedBy = 1;
            dt.CreatedOn = DateTime.Now;
            dt.OS = ""+1;
            dt.Browser = ""+1;
            dt.DeptStat = true;
            dt.IP = ""+1;

            testingtranscationAdd(dt);
             testingtranscationupdate(dt);
            return View();
        }

//in BLL Layer  the two mthods splits like that in DLL also

        public void testingtranscationAdd(LbMsDepartment dt)
        {
            dt.DeptName = "tested";
            dt.DeptDesc = "transaction testing";
            hms.LbMsDepartments.Add(dt);
            int i = hms.SaveChanges();

        }

   public void testingtranscationupdate(LbMsDepartment dt)
        {
            dt.DeptName = "tested";
            dt.DeptDesc = "transaction testing";
            hms.LbMsDepartments.Add(dt);
            int i = hms.SaveChanges();

        }

In the above code i want apply transaction based approch .