Read form authentication cookie from asp.net code behind

You can access the ticket with the Decrypt method provided by FormsAuthentication

HttpCookie authCookie = Request.Cookies[FormsAuthentication.FormsCookieName];
FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(authCookie.Value);

string cookiePath = ticket.CookiePath;
DateTime expiration = ticket.Expiration;
bool expired = ticket.Expired;
bool isPersistent = ticket.IsPersistent;
DateTime issueDate = ticket.IssueDate;
string name = ticket.Name;
string userData = ticket.UserData;
int version = ticket.Version;