public ActionResult Save(StudentGroup model)
        {
            try
            {
                string msg = model.Validate();
                if (!string.IsNullOrEmpty(msg))
                {
                    ViewBag.Message = msg;
                    return(View("Edit", model));
                }
                using (DataContext ctx = new DataContext())
                {
                    if (model.Id != 0)
                    {
                        var item = ctx.StudentGroup.FirstOrDefault(t => t.Id == model.Id);
                        item.Name = model.Name;
                    }
                    else
                    {
                        ctx.StudentGroup.Add(model);
                    }

                    ctx.SaveChanges();
                    return(RedirectToAction("Index"));
                }
            }
            catch (Exception ex)
            {
                ViewBag.Message = ex.Message;
                return(Edit(model.Id));
            }
        }