Trying to stream a PDF file with asp.net is producing a "damaged file"

Question

In one of my asp.net web applications I need to hide the location of a pdf file being served to the users.

Thus, I am writing a method that retrieves its binary content from its location on a CMS system and then flushes a byte array to the web user.

I'm getting, unfortunately, an error when downloading the stream: "Could not open the file because it is damadged" (or something similar to that, when opening the file in adobe reader).

Question 1: what am I doing wrong? Question 2: can I download large files using this approach?

    private void StreamFile(IItem documentItem)
    {
        //CMS vendor specific API
        BinaryContent itemBinaryContent = documentItem.getBinaryContent();
        //Plain old .NET
        Stream fileStream = itemBinaryContent.getContentStream();
        var len = itemBinaryContent.getContentLength();
        SendStream(fileStream, len, itemBinaryContent.getContentType());
    }

    private void SendStream(Stream stream, int contentLen, string contentType)
    {
        Response.ClearContent();
        Response.ContentType = contentType;
        Response.AppendHeader("content-Disposition", string.Format("inline;filename=file.pdf"));
        Response.AppendHeader("content-length", contentLen.ToString());
        var bytes = new byte[contentLen];
        stream.Read(bytes, 0, contentLen);
        stream.Close();
        Response.BinaryWrite(bytes);
        Response.Flush();
    }

Answer 1

Here is a method I use. This passes back an attachment, so IE produces an Open/Save dialog. I also happen to know that the files will not be larger than 1M, so I'm sure there's a cleaner way to do this.

I had a similar problem with PDFs, and I realized that I absolutely had to use Binary streams and ReadBytes. Anything with strings messed it up.

Stream stream = GetStream(); // Assuming you have a method that does this.
BinaryReader reader = new BinaryReader(stream);

HttpResponse response = HttpContext.Current.Response;
response.ContentType = "application/pdf";
response.AddHeader("Content-Disposition", "attachment; filename=file.pdf");
response.ClearContent();
response.OutputStream.Write(reader.ReadBytes(1000000), 0, 1000000);

// End the response to prevent further work by the page processor.
response.End();