返回内存流 - 提供损坏的PDF文件或"无法访问已关闭的流"

Question

我有一个Web服务,它调用以下方法.我想返回一个内存流,这是一个PDF文件.

现在,问题是PDF文件已损坏,代码如下.我认为这是因为文件没有被关闭.但是,如果我关闭它们,我会收到经典错误"无法访问已关闭的流".

当我之前通过文件流保存它时,PDF文件没有损坏.

所以我的谦虚问题是:如何解决它并找回一个未损坏的PDF文件？:-)

我的代码:

public Stream Generate(GiftModel model)
{
    var template = HttpContext.Current.Server.MapPath(TemplatePath);

    // Magic code which creates a new PDF file from the stream of the other
    PdfReader reader = new PdfReader(template);
    Rectangle size = reader.GetPageSizeWithRotation(1);
    Document document = new Document(size);

    MemoryStream fs = new MemoryStream();
    PdfWriter writer = PdfWriter.GetInstance(document, fs);
    document.Open();

    // Two products on every page
    int bookNumber = 0;
    int pagesWeNeed = (int)Math.Ceiling(((double)model.Books.Count / (double)2));
    for (var i = 0; i < pagesWeNeed; i++)
    {
        PdfContentByte cb = writer.DirectContent;

        // Creates a new page
        PdfImportedPage page = writer.GetImportedPage(reader, 1);
        cb.AddTemplate(page, 0, 0);

        // Add text strings
        DrawGreetingMessages(model.FromName, model.ReceiverName, model.GiftMessage, cb);

        // Draw the books
        DrawBooksOnPage(model.Books.Skip(bookNumber).Take(2).ToList(), cb);

        // Draw boring shit
        DrawFormalities(true, model.GiftLink, cb);

        bookNumber += 2;
    }

    // Close off our streams because we can
    //document.Close();
    //writer.Close();
    reader.Close();

    fs.Position = 0;
    return fs;
}

Answer 1

重用流可能会有问题,特别是如果您使用抽象并且您不太清楚它对您的流做了什么.因此我通常建议不要自己传递溪流.如果可以使用它,请尝试传递原始底层字节数组本身.但是如果需要传递流,那么我建议仍然在最后执行原始字节数组,然后将其包装在新的第二个流中.尝试以下代码,看看它是否有效.

public Stream Generate(GiftModel model)
{
    //We'll dump our PDF into these when done
    Byte[] bytes;

    using (var ms = new MemoryStream())
    {
        using (var doc = new Document())
        {
            using (var writer = PdfWriter.GetInstance(doc, ms))
            {
                doc.Open();
                doc.Add(new Paragraph("Hello"));
                doc.Close();
            }
        }
        //Finalize the contents of the stream into an array
        bytes = ms.ToArray();
    }
    //Return a new stream wrapped around our array
    return new MemoryStream(bytes);
}