Web API Accept type

[Greg Keogh]

Folks, in Web API when you sent an object back in the response it's
automatically serialized as JSON or XML depending upon the Accept header.
This is great, but I have to cheat the system slightly and send back
manually tweaked XML only if the XML serializer is "active". Rather than
look at the raw text of the request Accept headers, is there is more formal
way of knowing which serializer is "active" (if this means anything) -- *GK*