title: Returning File() returns more bytes
body: <p>Consider the following code:</p>
  
  <pre><code>//get bytes
  var query = await _storage.Get(attachment.Id, General.ContainerType.Uploads);
  //just for the sake of debugging
  var mem = new MemoryStream(query);
  //return the uploaded file
  return File(mem, MimeTypesMap.GetMimeType(attachment.FileName), attachment.FileName);
  </code></pre>
  
  <p>After uploading a .jpg image of 67kb and then downloading it with this method, the returned image is 107 kb. I have checked whether the bytes are stored and retrieved correctly and they indeed are constistent with what I have uploaded.  If I upload a text file and return it the content and the size is correct.</p>
  
  <p>I assume File() does some magic, but I can't figure out why and what?</p>