title: Encrypt a file using File.Encrypt and then Decrypt it to memory stream
body: <p>I need to implement a simple file encryption and then decrypt it, when needed, to a memory stream.
  The easiest way seems to do this with File.Encrypt, but is it possible to decrypt the file to memory stream, instead of decrypting the file before reading it to memory stream, and thus exposing it for a while?</p>
  
  <p>And if File.Encrypt is not the best way for this scenario, what would you recommend?</p>