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根据此处评论中的建议，我重构了我的方法以尝试将数据分配给 iTextSharp.text.Document “使用”之外的 MemoryStream（但在 MemoryStream using 子句中）：

internal static HttpResponseMessage GeneratePDFOfReportFutures()
{
    HttpResponseMessage result = null;
    futureReports = GetAllFutureReports();
    try
    {
        using (var ms = new MemoryStream())
        {
            using (var doc = new Document(PageSize.A4.Rotate(), 25, 25, 25, 25)) // the "Rotate" makes it landscape orientation
            {
                using (PdfWriter.GetInstance(doc, ms))
                {
                    doc.Open();
                    . . .
                    // "int i" is for testing a quick exit of this long-running loop
                    int i = 0;
                    foreach (QueuedReports qr in futureReports)
                    {
                        var tblRow = new PdfPTable(6)
                        {
                            WidthPercentage = 80,
                            SpacingBefore = 4f
                        };
                        float[] tblRowWidths = new float[] { 220f, 180f, 220f, 160f, 160f, 340f };
                        tblRow.SetWidths(tblRowWidths);
                        tblRow.HorizontalAlignment = Element.ALIGN_LEFT;

                        var phraseRptName = new Phrase(qr.ReportName, helvetica9);
                        var cellRptName = GetCellForBorderedTable(phraseRptName, Element.ALIGN_CENTER, BaseColor.WHITE);
                        cellRptName.VerticalAlignment = Element.ALIGN_MIDDLE;
                        tblRow.AddCell(cellRptName);

                        . . .
                        tblRow.AddCell(cellRecipients);

                        doc.Add(tblRow);

                        i++;
                        if (i >= 12)
                        {
                            break;
                        }
                    } // foreach
                } // pdfWriter
            } // doc
            var bytes = ms.ToArray();
            result = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new ByteArrayContent(bytes)
            };
            result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
            {
                FileName = string.Format("{0}.pdf", "test")
            };
            result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        } // memoryStream               
    } // try
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
    return result;
} // GeneratePDFOfReportFutures

使用“break”行中的断点，我执行 (F10) 并在到达字节分配之前捕获以下异常：

System.ObjectDisposedException 被捕获 HResult=-2146232798
Message= Cannot access a closed Stream。Source=mscorlib
ObjectName="" StackTrace：在 System.IO.__Error.StreamIsClosed() 在 System.IO。MemoryStream .Write(Byte[] buffer, Int32 offset, Int32 count) at iTextSharp.text.pdf.OutputStreamCounter.Write(Byte[] buffer, Int32 offset, Int32 count) at iTextSharp.text.pdf.PdfIndirectObject.WriteTo(Stream os ) 在 iTextSharp.text.pdf。PdfWriteriTextSharp.text.pdf.PdfWriter.PdfBody.Add(PdfObject objecta, Int32 refNumber, Int32 generation, Boolean inObjStm) 在 iTextSharp.text.pdf.PdfWriter.PdfBody 的 .PdfBody.Write(PdfIndirectObject 间接，Int32 refNumber，Int32 生成)。 Add(PdfObject objecta, PdfIndirectReference refa, Boolean inObjStm) at iTextSharp.text.pdf.PdfWriter.PdfBody.Add(PdfObject objecta, PdfIndirectReference refa) at iTextSharp.text.pdf.PdfWriter.AddToBody(PdfObject objecta, PdfIndirectReference refa) at iTextSharp。 text.pdf.Type1Font.WriteFont(PdfWriter writer, PdfIndirectReference piref, Object[] parms) at iTextSharp.text.pdf.FontDetails.WriteFont(PdfWriter writer) at iTextSharp.text.pdf.PdfWriter.AddSharedObjectsToBody() at iTextSharp.text。 iTextSharp.text 处的 pdf.PdfWriter.Close()。DocWriter.Dispose()

由于访问 PdfWriter 和/或 Doc 似乎是导致问题的原因，看来我不仅需要在 doc 使用中移动编写代码，还需要在 pdfWriter 使用中移动，所以我这样做了，像这样移动代码：

                . . .
                } // foreach
                var bytes = ms.ToArray();
                result = new HttpResponseMessage(HttpStatusCode.OK)
                {
                    Content = new ByteArrayContent(bytes)
                };
                result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
                {
                    FileName = string.Format("{0}.pdf", "test")
                };
                result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
            } // pdfWriter
        } // doc
    } // memoryStream               
} // try
catch (Exception ex)
{
    Console.WriteLine(ex.Message);
}
return result;

...但我仍然得到完全相同的例外。但是，我现在看到的内容与上一篇文章中描述的内容之间存在差异，因为直到 I F10 在此行上才会引发异常：

} // pdfWriter

如果我将返回线移到上方（并且仍然保持在 catch 块下方），如下所示：

    return result;
} // pdfWriter

...在“返回结果”行的 F10ing 上引发异常。

为什么会失败，我该如何预防？

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