Different result while reading the FormsAuthenticationTicket

I have a two blocks of codes which are supposed to do the same job, that is copying the whole FormsAuthenticationTicket and changing one bit of it which is stored in UserData.

The first code reads correctly everything including UserData. The second does not include UserData. It simply returns an empty string. I realised that when an exception was thrown because if an empty object.

Any idea?

The first code:

string cookieName = FormsAuthentication.FormsCookieName;
HttpCookie authCookie = HttpContext.Request.Cookies[cookieName];
if (authCookie != null)
{
    FormsAuthenticationTicket oldTicket = FormsAuthentication.Decrypt(authCookie.Value);
    UserData userDataObj = JsonConvert.DeserializeObject<UserData>(oldTicket.UserData);
    userDataObj.PassChangeRequired = user.PasswordChangeRequired;
    string userdata = JsonConvert.SerializeObject(userDataObj);
    FormsAuthenticationTicket newTicket = new FormsAuthenticationTicket(
                                                oldTicket.Version,
                                                oldTicket.Name,
                                                oldTicket.IssueDate,
                                                oldTicket.Expiration,
                                                oldTicket.IsPersistent,
                                                userdata,
                                                oldTicket.CookiePath);
    authCookie.Value = FormsAuthentication.Encrypt(newTicket);
    Response.Cookies.Set(authCookie);
}

The second code:

HttpCookie authCookie = FormsAuthentication.GetAuthCookie(user.UserName, false);
if (authCookie != null)
{
    FormsAuthenticationTicket oldTicket = FormsAuthentication.Decrypt(authCookie.Value);
    UserData userDataObj = JsonConvert.DeserializeObject<UserData>(oldTicket.UserData);
    userDataObj.PassChangeRequired = user.PasswordChangeRequired;
    string userdata = JsonConvert.SerializeObject(userDataObj);
    FormsAuthenticationTicket newTicket = new FormsAuthenticationTicket(
                                                oldTicket.Version,
                                                oldTicket.Name,
                                                oldTicket.IssueDate,
                                                oldTicket.Expiration,
                                                oldTicket.IsPersistent,
                                                userdata,
                                                oldTicket.CookiePath);
    authCookie.Value = FormsAuthentication.Encrypt(newTicket);
    Response.Cookies.Set(authCookie);
}

If you look at the MSDN for the GetAuthCookie() method that you use in example 2, you will see that it says:

Creates an authentication cookie for a given user name.

What this means is that when you make this call in example 2, you are actually getting back a brand new authentication cookie that was just created and not the one that you have already set. This is why the UserData property is empty/null.