[HttpPost]

        public IActionResult ImportTeaching(IFormFile file)

        {

            string root = @"Temp/teachingfile/";

            string phyPayh = evn.MapPath(root);

            if (file != null)

            {

                var parsedContentDisposition = ContentDispositionHeaderValue.Parse(file.ContentDisposition);

                var originalName = parsedContentDisposition.FileName.Replace("\"", "");

                file.SaveAs(phyPayh + originalName);

            }

            else

            {

                ModelState.AddModelError("", "没有选择文件");

                return View();

            }

            return RedirectToAction("Index");

        }

  [FromServices]

        public IHostingEnvironment evn { set; get; }