Topic: AuthenticationServiceClient (the first time works only)

I can not understand in what a problem, I use a standard authentication mechanism System.Web.ApplicationServices.AuthenticationService I Do it in such a way: string sharedCookie; using (AuthServiceReference.AuthenticationServiceClient clientAuth = new AuthServiceReference.AuthenticationServiceClient ()) {using (new OperationContextScope (clientAuth. InnerChannel)) {bool isLogin = clientAuth. Login ("UserName", "UserPass", string.empty, false); HttpResponseMessageProperty response = (HttpResponseMessageProperty) OperationContext.Current.IncomingMessageProperties [HttpResponseMessageProperty. Name]; sharedCookie = response. Headers ["Set-Cookie"];}} I use this  further, and there all apprx. But it works only once if I the second time cause it and I will receive  - that the second  does not work, in what there can be a business? After studio/rebilda restarting, again it is possible to fulfill once, and again the second  does not work.