after successful login, please keep the user's idenetiy to
var identity = new GenericIdentity(ticket.Name);
So, you have to follow forms authenticaion and this is right approach to solve your problem.
Please look at the FormAuthetication process in ASP.Net MVC. below is an example of log in method.
var ticket = new FormsAuthenticationTicket(...............
);
var encryptedTicket = FormsAuthentication.Encrypt(ticket);
var cookie = new HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket)
{
HttpOnly = true,
Secure = FormsAuthentication.RequireSSL
};
var identity = new GenericIdentity(ticket.Name);
HttpContext.Current.User = identity;