.net core5.0 ICSharpCode.SharpZipLib.Core stream 导出Zip

1	`using` `ICSharpCode.SharpZipLib.Core;`

public FileResult ExportAll(int gradeId)
       {
 
           var zipObjects = _scoreImportService.ExportAll(gradeId);
 
           var outputMemoryStream = new MemoryStream();
           var zipStream = new ZipOutputStream(outputMemoryStream);
 
           zipStream.SetLevel(3);
 
           foreach (var item in zipObjects)
           {
               var data = item.XlsDataTable;
               var buffer = data.SaveToMemoryStream("学生成绩");
 
               var inputMemoryStream = new MemoryStream(buffer.ToArray());
               var zipEntry = new ZipEntry($"{item.Name}.xls");
               zipEntry.DateTime = DateTime.Now;
 
               zipStream.PutNextEntry(zipEntry);
               StreamUtils.Copy(inputMemoryStream, zipStream, new byte[4096]);
               zipStream.CloseEntry();
           }
 
           zipStream.IsStreamOwner = false;
           zipStream.Close();
 
           outputMemoryStream.Position = 0;
 
           //return outputMemoryStream.ToArray();
 
 
           var fileName = "全部";
           if (gradeId != -1)
           {
               fileName = gradeId + "届";
           }
           return File(outputMemoryStream, "application/zip;charset=UTF-8", fileName + "学生成绩单.zip");
       }