使用 ITextSharp 将 PDF 导出到目录时损坏的文件

Question

I am trying to generate a PDF using ITextSharp, but when I try to open it, it states it's corrupt:

Everything seems to work fine until I open it up.

Code:

using (MemoryStream ms = new MemoryStream())
{
    Document document = new Document(PageSize.LETTER, 30, 30, 5, 5);
    PdfWriter writer = PdfWriter.GetInstance(document, ms);
    document.Open();

     // Style Code 

    #endregion

    document.Close();
    writer.Close();

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new ByteArrayContent(ms.GetBuffer())
    };

    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
    result.Content.Headers.ContentDisposition.FileName = filename;
    string filePath = @"C:\Users\mmaslova\Desktop\TEMP\" + filename;
    FileStream stream = new FileStream(filePath, FileMode.Create);

    return result;
}

Answer 1

Here is one error:

    Content = new ByteArrayContent(ms.GetBuffer())

MemoryStream.GetBuffer() returns the whole buffer which may be much larger than the actual content. Thus, your Content often will contain a PDF with a tail of a lot of garbage bytes. As a PDF processor is expected to read a PDF from its end (where a reference to object cross references can be found), it tries to find that reference at the end of your garbage bytes. This fails, so the file is corrupt. (Actually Adobe Reader and other processors following its lead look for that reference in the last 1024 bytes of the file. This increases the chances of finding it but there still are enough situations in which the reference won't be found.)

You essentially have two choices:

• Either you use MemoryStream.ToArray() instead. This method returns only the actual content, not unused trailing bytes. The disadvantage: It creates a copy of those bytes. Depending on the size of your PDFs and your resources, that might mean trouble.
• Or you use MemoryStream.GetBuffer() only with methods which also accept a parameter denoting the length of the actual content in that byte array, and set that parameter to MemoryStream.Length .

Eg in your case ByteArrayContent also has a constructor

public ByteArrayContent (byte[] content, int offset, int count);

( Microsoft docs on ByteArrayContent )

so you can replace

    Content = new ByteArrayContent(ms.GetBuffer())

by

    Content = new ByteArrayContent(ms.GetBuffer(), 0, ms.Length)

Answer 2

The answer was that I needed to move the FileStream before document.Open();

Answer:

using (MemoryStream ms = new MemoryStream())
{
     Document document = new Document(PageSize.LETTER, 30, 30, 5, 5);
     PdfWriter writer = PdfWriter.GetInstance(document, ms);

     string filePath = @"C:\Users\mmaslova\Desktop\TEMP\" + filename;
     PdfWriter.GetInstance(document, new FileStream(filePath, FileMode.Create));
     document.Open(); 

     #endregion

    document.Close();
    writer.Close();

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
    
       Content = new ByteArrayContent(ms.GetBuffer())
  
    };

    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
    result.Content.Headers.ContentDisposition.FileName = filename;

    return result;

}