Clicking Open Word Document tries to reconnect to Controller action while downloading - asp.net-mvc-3

Question

I have a requirement to download a file from the server, but open inline if possible. I'm currently doing;
Response.AddHeader("Content-Disposition", string.Format("inline; filename={0}", documentFileName));
result = new FileStreamResult(new FileStream(documentFilePath, FileMode.Open), "application/msword");
I've put application/msword in there right now, because that's what I'm having a problem with. When I click Open on the word document, it's as if the document makes multiple calls back to the action, but there is no session and no database so it crashes. When the user is running this, they see a long hang, the "Downloading" dialog finally appears in word and they have to cancel it. The document is there and is valid but this is not desirable.
Pdfs, pngs etc. download fine. Can anybody explain this behavior, and give me some hints as to how I fix it?
Update:
The action basically looks like;
[HttpPost]
public FileResult View(int id, int source)
{
var document = GetDocumentFromDatabase(id, source);
documentFilePath = Path.Combine( documentsDirectory, document.Name);
documentName = document.Name;
Response.AddHeader("Content-Disposition", string.Format("inline; filename={0}", documentFileName));
result = new FileStreamResult(new FileStream(documentFilePath, FileMode.Open), "application/msword");
return result;
}
I've trimmed it down, as I can't share the specifics, but the full idea is there.
Answer:
I have a lookup of available content-types, in there I have defined whether the file is inline or attachment, and when I detect a word document, I set it to attachment. No more error. PDF opens in the browser still because I set it to inline.

Answer 1

I use:
public ActionResult GetAttachment(int id)
{
var attachment = _repository.GetAttachByID(id);
if (attachment != null)
{
Response.AppendHeader("Content-Disposition",string.Format("inline; filename={0}",attachment.FileName));
return File(attachment.File, attachment.MimeType, attachment.FileName);
}
else
{
return null;
}
}
Regards