iTextSharp file manipulation and display to FileStreamResults

I am trying top open a PDF file using iTextSharp, add a dataset to the file to prepopulate data, then save it to a stream so that I can display it to the users. I don't want to save it locally to a file. I keep getting the error "Cannot access a closed Stream." I can't figure out which stream is wrong.

Here is my code:

public FileStreamResult PushDataIntoPDFStream(string filename)
{     
     var reader = new PdfReader(Path.Combine(Server.MapPath(path), filename));
     var xml = @"<?xml version=""1.0"" encoding=""UTF-8""?>
          <form1>  
             <firstName>test</firstName>
             <lastName>user</lastName>
             <driveCar>0</driveCar>
             <gender>1</gender>
             <birthdate>2011-08-12</birthdate>
             <numPets>4</numPets>
          </form1>";

     using (var outstream = new MemoryStream())
     { 
          using (var stamper = new PdfStamper(reader, outstream))
          {
               var bytes = System.Text.Encoding.UTF8.GetBytes开发者_JAVA技巧(xml);
               using (var ms = new MemoryStream(bytes))
               {
                    stamper.AcroFields.Xfa.FillXfaForm(ms);
               }
          }

          return new FileStreamResult(outstream, "application/pdf")
          {
                FileDownloadName = "file.pdf";
          };
     }      
  }

---

The PdfStamper has a .CloseStream property on its internal output stream; try setting it to false:

using (var stamper = new PdfStamper(reader, outstream))
{
    stamper.Writer.CloseStream = false;