FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket(
            1,
            userName,
            DateTime.Now,
            DateTime.Now.AddMinutes(20),
            false,
            "admin"//写入用户角色
            );

        string encryptedTicket = FormsAuthentication.Encrypt(authTicket);

        System.Web.HttpCookie authCookie = new System.Web.HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket);
        System.Web.HttpContext.current.Response.Cookies.Add(authCookie);

PRotected void Application_AuthenticateRequest(Object sender, Eventargs e)
    {
        HttpCookie authCookie = Context.Request.Cookies[FormsAuthentication.FormsCookieName];
        if (authCookie == null || authCookie.Value == "")
        {
            return;
        }
        FormsAuthenticationTicket authTicket = null;
        try
        {
            authTicket = FormsAuthentication.Decrypt(authCookie.Value);
        }
        catch
        {
            return;
        }
        string[] roles = authTicket.UserData.SplIT(new char[] { ';' });
         if (Context.User != null)
        {
            Context.User = new System.Security.Principal.GenericPrincipal(Context.User.Identity, roles);
        }
    }

　　[Authorize(Roles="admin")]
    public ActionResult Index(int ? page)