c# /ASP不能用pdf文件创建zip文件

我正在从数据库中抓取数据，转换它，试图将其压缩并返回给用户。我可以成功地为txt和docx文件创建一个zip文件，但如果我尝试使用pdf或zip文件，它会失败，并说文件无法下载。当试图从pdf创建zip文件时，您是否知道代码在哪里崩溃?

if (e.CommandName == "DownloadAttachment")
    {
        e.Canceled = true;
        var item = e.Item as GridEditableItem;
        fileId = (int)item.GetDataKeyValue("Unique");
        FileData[] allrecords = null;
        using (
            SqlConnection conn =
                new SqlConnection(ConfigurationManager.ConnectionStrings["PtcDbModelEntities"].ConnectionString))
        {
            using (
                SqlCommand comm = new SqlCommand("Select Unique1, BinaryData, FileName from PtcDbTracker.dbo.CafFileTable where Unique1=@fileId AND FileName IS NOT NULL", conn))
            {
                comm.Parameters.Add(new SqlParameter("@fileId", fileId));
                conn.Open();
                using (var reader = comm.ExecuteReader())
                {
                    var list = new List<FileData>();
                    while (reader.Read())
                    {
                        long len = reader.GetBytes(1, 0, null, 0, 0);
                        Byte[] buffer = new byte[len];
                        list.Add(new FileData { BinaryData = buffer, FileName = reader.GetString(2) });
                        allrecords = list.ToArray();
                    }
                }
                conn.Close();
            }
        }
        using (var compressedFileStream = new MemoryStream())
        {
            HttpContext context = HttpContext.Current;
            HttpResponse response = context.Response;
            using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Update, true))
            {
                if (allrecords != null)
                {
                    foreach (var record in allrecords)
                    {
                        if (record.FileName != null)
                        {
                            ZipArchiveEntry zipEntry = zipArchive.CreateEntry(record.FileName, CompressionLevel.NoCompression);
                            using (var zipEntryStream = zipEntry.Open())
                            {
                                zipEntryStream.Write(record.BinaryData, 0, record.BinaryData.Length);
                                zipEntryStream.Dispose();
                            }
                        }
                    }
                }
                zipArchive.Dispose();
            }
            compressedFileStream.Close();
            response.Clear();
            response.ClearContent();
            response.ClearHeaders();
            response.BufferOutput = true;
            response.AppendHeader("Content-Type", "Application/zip");
            response.AppendHeader("Content-Disposition", "Attachment; filename=result.zip");
            response.BinaryWrite(compressedFileStream.ToArray());
            response.Flush();
            response.SuppressContent = true;
            context.ApplicationInstance.CompleteRequest();
            response.Close();
        }
    }