WCF Transport Security with SSL and Thread information

I have a question about the above topic. I have a WCF service and use the Transport security model for it. But there is some mechanism related to the Thread state that I can't understand. In constructor of my service I tried to set the Thread.CurrentPrincipal but at the begin of a called method of my service the Thread.CurrentPrincipal became null... I read that it can be in case of usage WC开发者_JAVA百科F Transport Security.

Is the reason in WCF Transport Security or is there any other reason for this behavior?

Thanks in advance! Sorry for confusions in the explanation if there are some.

Does this help: http://connect.microsoft.com/VisualStudio/feedback/details/369445/wcf-service-configured-for-transport-security-shouldnt-change-thread-currentprincipal