使用WebAPI 2响应中的ItextSharp在下载的PDF上的空内容

Question

public IHttpActionResult DownloadPDF()
{
    var stream = CreatePdf();
    return ResponseMessage(new HttpResponseMessage
    {
        Content = new StreamContent(stream)
        {
            Headers =
            {
                ContentType = new MediaTypeHeaderValue("application/pdf"),
                ContentDisposition = new ContentDispositionHeaderValue("attachment")
                {
                    FileName = "myfile.pdf"
                }
            }
        },
        StatusCode = HttpStatusCode.OK
    });
}
Here is the CreatePdf method:
private Stream CreatePdf()
{
    using (var document = new Document(PageSize.A4, 50, 50, 25, 25))
    {
        var output = new MemoryStream();
        var writer = PdfWriter.GetInstance(document, output);
        writer.CloseStream = false;
        document.Open();
        document.Add(new Paragraph("Hello World"));
        document.Close();
        output.Seek(0, SeekOrigin.Begin);
        return output;
    }
}

我能够下载PDF，但上下文是空的。在这里，我正在使用内存流，还尝试使用文件流在各自的文件夹中下载其下载，但是如果我尝试打开下载的文件，则内容也为空。谁能帮我这里想念的东西？

Answer 1

这是一种通常在使用Web API

时对我有用的方法

private byte[] CreatePdf() {
    var buffer = new byte[0];
    //stream to hold output data
    var output = new MemoryStream();
    //creation of a document-object
    using (var document = new Document(PageSize.A4, 50, 50, 25, 25)) {
        //create a writer that listens to the document
        // and directs a PDF-stream to output stream
        var writer = PdfWriter.GetInstance(document, output);
        //open the document
        document.Open();
        // Create a page in the document
        document.NewPage();
        // Get the top layer to write some text
        var pdfContentBytes = writer.DirectContent;
        pdfContentBytes.BeginText();
        //add content to page
        document.Add(new Paragraph("Hello World"));
        //done writing text
        pdfContentBytes.EndText();
        // make sure any data in the buffer is written to the output stream
        writer.Flush();
        document.Close();
    }    
    buffer = output.GetBuffer();
    return buffer;
}

，然后在动作中

public IHttpActionResult DownloadPDF() {
    var buffer = CreatePdf();
    return ResponseMessage(new HttpResponseMessage {
        Content = new StreamContent(new MemoryStream(buffer)) {
            Headers = {
                ContentType = new MediaTypeHeaderValue("application/pdf"),
                ContentDisposition = new ContentDispositionHeaderValue("attachment") {
                    FileName = "myfile.pdf"
                }
            }
        },
        StatusCode = HttpStatusCode.OK
    });
}