问当我试图更新时，我的图像url返回为null。

EN

ublic IActionResult Upsert(ProductVM obj,IFormFile file)
        {
            if (ModelState.IsValid)
            {
                string wwwRootPath = _hostEnvironment.WebRootPath;
                if (file != null)
                {
                    string fileName = Guid.NewGuid().ToString();
                    var uploads = Path.Combine(wwwRootPath, @"Images\products");
                    var extention = Path.GetExtension(file.FileName);
                    if (obj.Product.ImageUrl != null)
                    {
                        var oldImagePath = Path.Combine(wwwRootPath,obj.Product.ImageUrl.TrimStart('\\'));
                        if (System.IO.File.Exists(oldImagePath))
                        {
                            System.IO.File.Delete(oldImagePath);
                        }
                    }
                    using (var fileStreams = new FileStream(Path.Combine(uploads, fileName + extention), FileMode.Create))
                    {
                        file.CopyTo(fileStreams);
                    }
                    obj.Product.ImageUrl = @"\Images\products\" + fileName + extention;
                }
                if (obj.Product.Id == 0)
                {
                    _unitOfWork.Product.Add(obj.Product);
                }
                else
                {
                    _unitOfWork.Product.Update(obj.Product);
                }
                    _unitOfWork.Save();
                TempData["success"] = "Produs adaugat cu succes!";
                return RedirectToAction("Index");
            }
                    return View(obj);
        }