Multipart image upload

Hello

I've been hitting a wall on this issue. Can anyone point me in the right direction to upload a an image to a server using a multipart message (the message needs to work this way, I cannot change the API), which should look something like this.

Content‐Type:multipart/mixed

Content-ID: root Content-Type: application/json [JSON MESSAGE GOES HERE]

Content-ID: images Content-Type: image/jpeg [Byte array goes here]

Now, I've been using UniWeb for talking to this API, and that handles the headers and all that stuff, but I can't do this out of the box, so I need some help building my own request.

any ideas?

P.s. I cannot use HttpWebRequest because this could potentially be output to the web player, which does not support it.