Question

我正在使用Magick.NET将PDF转换为PNG并通过ajax将其流回页面。

一直有效，直到PDF上传两次。尝试覆盖或删除现有文件时，调试器会告诉我该文件正被另一个进程使用。

这是我的函数，它将Image返回给控制器：

    //path is a fully qualified path to a file ending in .PDF
    private Image ConvertPDFTOneImage(string path)
    {
        MagickReadSettings settings = new MagickReadSettings();
        settings.Density = new PointD(300, 300);

        using (MagickImageCollection images = new MagickImageCollection())
        {
            FileInfo file = new FileInfo(path);
            images.Read(file);
            file = null;

            using (MagickImage horizontal = images.AppendHorizontally())
            {
                string PNGName = Path.ChangeExtension(path, ".png");
                horizontal.Write(PNGName);
            }

            return Image.FromFile(path.Replace("pdf", "png"));
        }
    }

我的控制器将响应流回浏览器：

 public async Task<HttpResponseMessage> PostFormData([FromUri] int sellerID, [FromUri] int eventID, [FromUri] string section, [FromUri] string row, [FromUri] string seat)
        {
            if (HttpContext.Current.Request.Files.AllKeys.Any())
            {
                try
                {
                    string base64 = string.Empty;
                    SellerObjects.Externeal.SellerTicket TicketToSave = new SellerObjects.Externeal.SellerTicket();

                    TicketToSave.UploadedFile = HttpContext.Current.Request.Files["UploadedImage"];
                    SellerTicketRepo TheLocalSellerRepo = new SellerTicketRepo(TicketToSave);

                    using (MemoryStream ms = new MemoryStream())
                    {
                        TheLocalSellerRepo.GetConvertedPDFImage().Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                        base64 = System.Convert.ToBase64String(ms.ToArray());
                    }

                    HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
                    result.Content = new StringContent(base64);
                    result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/png");
                    return result;
                }
                catch (Exception ex)
                {
                    return Request.CreateResponse(HttpStatusCode.BadRequest, "Error saving file.");
                }
            }

            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "An error has occurred");
        }

Answer 1

我假设您要返回的Image类是System.Drawing.Image。您需要Dispose此对象以释放文件锁。

// Instead of this:
using (MemoryStream ms = new MemoryStream())
{
  TheLocalSellerRepo.GetConvertedPDFImage().Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
  base64 = System.Convert.ToBase64String(ms.ToArray());
}

// Should you be doing this:
using (MemoryStream ms = new MemoryStream())
{
  using (Image img = TheLocalSellerRepo.GetConvertedPDFImage())
  {
    img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    base64 = System.Convert.ToBase64String(ms.ToArray());
  }
}

// Or you could even do this (if GetConvertedPDFImage() returns a MagickImage):
using (MagickImage img = TheLocalSellerRepo.GetConvertedPDFImage())
{
  img.Format = MagickFormat.Jpeg;
  base64 = img.ToBase64();
}

无法删除已创建和流式文件

1 个答案: