Can I save twice to the same stream?

[Aaron]

Q:

I'm signing a document twice, and each time saving to a memory stream incrementally.  My code looks something like this:

using (var ms = new MemoryStream())
{
  using (PDFDoc doc = new PDFDoc(infile))
  {
    // [...sign the document...]
    doc.Save(ms, 0);
  }
  ms.Position = 0;
  using (var doc = new PDFDoc(ms))
  {
    // [...sign the document with a second signature...]
    doc.Save(ms, SDFDoc.SaveOptions.e_incremental);
    // [...save ms to file...]
  }
}

The save after the second signature results in a corrupted file.  What's going wrong?



A:

You should save to a second stream different than the one you loaded the PDF from.  For example:

using (var ms = new MemoryStream())
{
  using (PDFDoc doc = new PDFDoc(infile))
  {
    // [...sign the document...]
    doc.Save(ms, 0);
  }
  ms.Position = 0;
  using (var doc = new PDFDoc(ms))
  {
    // [...sign the document with a second signature...]
    using (var ms1 = new MemoryStream())
    {
      doc.Save(ms1, SDFDoc.SaveOptions.e_incremental);
      // [...save ms1 to file...]
    }
  }
}