如果在POST方法中 UploadImage 的值不是 null ，则假设您要删除当前文件，然后你可以使用 System.IO.File.Delete 方法

Assuming you want to delete the current file if the value of UploadImage is not null in the POST method, then you can use the System.IO.File.Delete method

private const string _ImagesPath = "~/Images/Carousel";

[HttpPost]
public ActionResult EditCarousel(Carousel carousel, HttpPostedFileBase UploadImage)
{
  if (ModelState.IsValid)
  {
    CarouselRepositories blCarousel = new CarouselRepositories();
    if (UploadImage != null)
    {
      // Delete exiting file
      System.IO.File.Delete(Path.Combine(Server.MapPath(_ImagesPath), carousel.CarouselImage));
      // Save new file
      string fileName = Guid.NewGuid() + Path.GetFileName(UploadImage.FileName);
      string path = Path.Combine(Server.MapPath(_ImagesPath), fileName);
      UploadImage.SaveAs(path)
      carousel.CarouselImage = fileName;
    }
    if (blCarousel.Update(carousel))
    {
      ....
    }
    else
    {
      ....
    }
  }
  else
  {
    ....
  }
}