FormsAuthentication isn't preserving the UserData field after Postback in .NET 3.5

I've created a FormsAuthenticationTicket from scratch, but found that when retrieving it at a later time, the UserData isn't coming back. Here is the code used:

FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(

HttpCookie cookie = new HttpCookie(


However, when reading this back on the next Request, I found that the UserData field is now empty:

string encryptedCookie = Request.Cookies[ FormsAuthentication.FormsCookieName ].Value;
FormsAuthenticationticket ticket = FormsAuthentication.Decrypt(encryptedCookie);
Assert.IsTrue( ticket.UserData.Length == 0 ); //TRUE!

Any ideas?


I think I found the problem. If you make up your own cookie name it seems to be fine! So change from:

HttpCookie cookie = new HttpCookie(


HttpCookie cookie = new HttpCookie(

And then retrieve it as per the question:

string encryptedCookie = Request.Cookies[ "SiteCookie" ].Value;
FormsAuthenticationticket ticket = FormsAuthentication.Decrypt(encryptedCookie);
Assert.IsFalse( ticket.UserData.Length == 0 ); //Hooray! It works

Its possible .NET does some tricky stuff with it, so by putting it in a new one works fine.


Also, the ticket needs to be refreshed, as otherwise the ticket will expire while the user is using the website:

FormsAuthentication.RenewTicketIfOld(ticket); // Do before saving cookie

This works for me:

//Create Form Authentication ticket
FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(1, currentUser.userid.ToString(), DateTime.Now, DateTime.Now.AddMinutes(60), false, currentUser.ToString(), FormsAuthentication.FormsCookiePath);

string hashCookies = FormsAuthentication.Encrypt(ticket);
HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, hashCookies);
cookie.HttpOnly = true;

I have also encountered this problem. But I think the real reason is that the server set the same cookie twice and the second override the first which contains your UserData field.

You can capture the cookie writing process by Fiddler, and here is a screenshot that show this problem:

So, how this happened? In my situation, I use the Login control to authenticate. In the Login control's Authenticate event, I set the cookie with my UserData after check the username and password manaully. Then, I set the AuthenticateEventArgs.Authenticated=true, at this time, in the debug window, I see a new cookie is queued to the response which name is also equal to FormsAuthentication.FormsCookieName ! My solution is redirect to the Default page instead of setting the AuthenticateEventArgs.Authenticated=true.

So, you may debug your code to see if the authentication cookie is queued to the response twice.

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