asp.net mvc3 and cookie

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C#

ASP.NET

MVC3

I have a website where a user can authenticate with their facebook account or twitter:
to know the user I used the cookie:

Global.asax:

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
        {
            HttpCookie authCookie = Request.Cookies[FormsAuthentication.FormsCookieName];
            if (authCookie != null)
            {
                var authTicket = FormsAuthentication.Decrypt(authCookie.Value);
                var id = new MyIdentity(authTicket);
                var userData = authTicket.UserData.Split(',');
               
                id.SocialProviderName = userData[0].Replace("providerslist=", "").Split('|')[0];
                var newUser = new MyPrincipal(id);
                Context.User = newUser;
            }

        }

the user can link two accounts (facebook and twitter). connect with
twitter and then click on "account linking" and will be redirect to authenticate with her facebook account

the problem is that when redirecting to the second account the cookie becomes null and

if (this.HttpContext.Request.IsAuthenticated)
            {...}

return false


My Controller:
....
FormsAuthentication.SetAuthCookie(socialProfile.UserId, true);
ResetFormsCookie(providerName, socialProfile.UserId);
....
UserId generate by GUID

public void ResetFormsCookie(string providerName, string userId)
        {
            var authCookie = HttpContext.Current.ApplicationInstance.Request.Cookies[FormsAuthentication.FormsCookieName];
            if (authCookie == null)
            {
                authCookie = FormsAuthentication.GetAuthCookie(userId, true);
            }
            var authTicket = FormsAuthentication.Decrypt(authCookie.Value);
            var userData = authTicket.UserData;
            var providerslist = (from c in userData.Split(',') where c.Contains("providerslist=") select c).FirstOrDefault();
            if (string.IsNullOrEmpty(providerslist))
            {
                userData += string.IsNullOrEmpty(userData) ? "providerslist=" + providerName : ",providerslist=" + providerName;
            }
            else
            {
                if (!providerslist.Contains(providerName))
                {
                    userData = userData.Replace(providerslist, providerslist + "|" + providerName);
                }
            }
            var newTicket = new FormsAuthenticationTicket(authTicket.Version, authTicket.Name, authTicket.IssueDate
                , DateTime.Now.AddDays(90) // authTicket.Expiration ToDo: This need to set in the config
            , authTicket.IsPersistent, userData);
            authCookie.Value = FormsAuthentication.Encrypt(newTicket);
            HttpContext.Current.Response.Cookies.Add(authCookie);
        }

I apologize for my English
Thanks,