c# – 合并XPS文件会将打开的文件句柄留给文档引用

我正在通过IIS Web应用程序合并XPS文件,但在合并过程中,它会使文档引用文件句柄处于打开状态.在 Windows WPF或控制台应用程序中,我不担心句柄,因为它们会在应用程序关闭后释放.回收应用程序池也会有效地关闭句柄.但是,由于缓存和性能,我无法仅仅为了关闭文件句柄而回收应用程序池.

合并完成后有没有办法关闭这些文件句柄？我尝试了一些不同的合并方法,但以下代码给了我最好的结果：

private DocumentPaginator CreateMergedDocument(IEnumerable<string> xpsFiles) {   
  using ( MemoryStream mergedStream = new MemoryStream() ) {
    using ( var pkg = Package.Open( mergedStream,FileMode.Create,FileAccess.ReadWrite ) ) {
      var pack = "pack://merged.xps";
      var uri = new Uri( pack,UriKind.Absolute );
      PackageStore.AddPackage( uri,pkg );
      using ( XpsDocument mergedDocument = 
          new XpsDocument( pkg,CompressionOption.Maximum,pack ) ) {
        FixedDocumentSequence seqNew = new FixedDocumentSequence();

        foreach ( string sourceDocument in xpsFiles ) {
          using ( XpsDocument xpsOld = 
              new XpsDocument( sourceDocument,FileAccess.Read ) ) {
            FixedDocumentSequence seqOld = xpsOld.GetFixedDocumentSequence();

            foreach ( DocumentReference dr in seqOld.References ) {
              DocumentReference newDocumentReference = new DocumentReference();
              newDocumentReference.Source = dr.Source;
              ( newDocumentReference as IUriContext ).BaseUri = 
              ( dr as IUriContext ).BaseUri;
              seqNew.References.Add( newDocumentReference );
            }
          }
        }

        XpsDocumentWriter xpsWriter = XpsDocument.CreateXpsDocumentWriter( mergedDocument );
        xpsWriter.Write( seqNew );

        PackageStore.RemovePackage( uri );

        return seqNew.DocumentPaginator;
      }
    }
  }
}

我找到了打开xpsWriter.Write(seqNew)代码行的文件句柄.这是预期的,因为它需要加载文件以复制到新的FixedDocumentSequence中.但是,如果XpsDocumentWriter是一次性的并清理其非托管资源/文件句柄,那将是很好的.

在我的研究期间,我尝试了其他一些方法.我尝试过的一种方法是将每个页面可视化写入SerializerWriterCollat??or.我研究的另一种方法是处理FixedPage内容并将URI更新为复制的图像和字体流,并将原始XAML写回XmlWriter.两者都没有奏效.使用页面视觉效果和SerializerWriterCollat??or,我在合并的XPS上获得了不正确的页面大小,并且它正在切断内容.使用原始XmlWriter方法,它在合并的XPS中混淆了一些图像并错误地显示了一些页面内容.

private static readonly TaskScheduler _staScheduler = new StaTaskScheduler( 1 );

[Route( "merge" )]
[HttpGet]
public async Task<HttpResponseMessage> MergeXps() {
  var paginator = await Task<DocumentPaginator>.Factory.StartNew(
    () =>
      {
        var xpsFiles = Directory.GetFiles( "C:Xps","*.xps" );
        var documentPaginator = CreateMergedDocument( xpsFiles );

        return documentPaginator;
      },CancellationToken.None,TaskCreationOptions.None,_staScheduler );

  var response = new HttpResponseMessage();
  response.Content = new StringContent( $"Merged Document Page Count: {paginator.PageCount}" );
  response.StatusCode = HttpStatusCode.OK;
  return response;
}