Fetch Value from Third Level Table

Question

I Have Three Table Linked with each other. I want to fetch Value from other table How do I write Code. I Try This but Variable 'mythkvalue' returns null value. How I will get value for mythkvalue

[HttpPost]
        public ActionResult CreateP3(Process process)
        {
            var tr = process.StageID + process.PIPENO + process.Status;
            var checkme = (from x in db.Processes
                           where x.StageID + x.PIPENO + x.Status == tr && x.Status == "OK"
                           select x).ToList();
            var mythkvalue = process.PipeAl.Order.THK;

            if (checkme.Count > 0)
            {
                ModelState.AddModelError("PIPENO", "You are trying Duplicate Pipe Entry");
            }
            if (ModelState.IsValid)
            {
                if (mythkvalue > 1)
                {
                    process.MPP = 25;
                }
                process.CuttingSpeed = (process.ActualMeter*1000)/process.CuttingTime;
                db.Processes.Add(process);
                db.SaveChanges();
                return RedirectToAction("IndexP3");
            }

            var EmpAtnList = db.Attens.ToList();
            IEnumerable<SelectListItem> AttnList = from s in EmpAtnList.OrderByDescending(s => s.ATTNDATE)
                                                   select new SelectListItem
                                                   {
                                                       Value = s.ATTNSYSID.ToString(),
                                                       Text = s.ATTNDATE + "--" + s.Emp.EmpName
                                                   };

            ViewBag.ATTNSYSID = new SelectList(AttnList, "Value", "Text");

            //ViewBag.ATTNSYSID = new SelectList(db.Attens, "ATTNSYSID", "EMPCODE", process.ATTNSYSID);
            ViewBag.StageID = new SelectList(db.OMStages, "StageID", "StageName");
            ViewBag.NextStageID = new SelectList(db.OMStages.OrderBy(x => x.StageValue), "StageID", "StageName");
            ViewBag.PIPENO = new SelectList(db.PipeAls, "PIPENO", "PIPENO");
            ViewBag.Status = new SelectList(db.ValueAddLists.Where(x => x.RefName == "PipeStatus"), "RefValue", "Description", process.Status);
            return View(process);
        }