wcf HMAC always fails
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I'm trying to implement a HMAC authorization solution with my SOAP WCF service. I already have a message inspector for the client and the server. The server seems to add a "Action" header to the message that is not in the request (verified by fiddler). I then just do 

message.WriteBodyContents(xdw);

Which gets around that but then some of the xml elements are self closed (/>) or some are closed like "</element>".

Any suggestions?

EDIT.
I also want the solution to be easy, so far this is all done with an attribute on the service and a one line statement for the client.