public ActionResult Create(CourseMaterial coursematerial)
        {
            if (ModelState.IsValid)
            {
                db.CourseMaterials.Add(coursematerial);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.ClassID = new SelectList(db.Courses, "ClassID", "ClassName", coursematerial.ClassID);
            return View(coursematerial);
        }
 public ActionResult Edit(CourseMaterial coursematerial)
 {
     if (ModelState.IsValid)
     {
         db.Entry(coursematerial).State = EntityState.Modified;
         db.SaveChanges();
         return RedirectToAction("Index");
     }
     ViewBag.ClassID = new SelectList(db.Courses, "ClassID", "ClassName", coursematerial.ClassID);
     return View(coursematerial);
 }