Does viewstate expire?

Question

Let's say you have a aspx page that does not rely on session, but does rely on viewstate for persistance between postbacks.

If a user is accessing this page, and leaves for a long lunch, will viewstate still be valid when he returns?

Answer 1

No ViewState is kept as part of the PostBack process. You can, however, override the Page class's SavePageStateToPersistenceMedium() and LoadPageStateFromPersistenceMedium(), to implement that behavior if desired. For more information read Understanding the ASP.NET ViewState.

Note that Page ViewState is stored in the Session so if your Session expires, the ViewState will be lost. I wouldn't say this is ViewState expiring, but yes, it will be destroyed after Session timeout.

Answer 2

Viewstate itself does not expire. Since it's posted back in a form, it can be reconstituted any time.

According to MSDN: "...it is possible for view state to expire if a page is not posted back within the session expiration time". So, in a round about sort of way, it can expire if your session does, but viewstate does not directly expire. Since you're not using session state anyway, you don't have to worry about implicit expiration.

Note that I wouldn't have said it expired. That was MS who I quoted in their own article entitled Controlling ViewState

Answer 3

Viewstate does not expire, as long as they are still on the page, it will still be there and functional.

Answer 4

Viewstate does not expire.

All viewstate data is stored on the client and is submitted back to the server when the user executes a postback.

This has some very interesting implications, and is explained very thoroughly here.

Answer 5

ViewState is kept in a hidden field on the page itself. So as long as the user has the page, he'll have the ViewState. But if your app automatically logs the user out after a certain period of time, still having the ViewState may not do him any good.

Answer 6

By default, Viewstate is included with the html content as a hidden input. That means it won't expire, but that everything in viewstate must be uploaded from the user's browser. Since that's typically the slowest part of the connection in a public site, putting a lot of stuff in viewstate can quickly make your site seem very slow.

Answer 7

The short answer is: no.

The longer answer is: it depends on implementation of ViewState storage. You can provide custom implementation of ViewState which could expire after given amount of time. For example, you could store ViewState in database or on disk and send only some reference to the stored value in a hidden field. Then you can use batch processing to remove outdated ViewState data or perform expiration upon request.

Answer 8

The ViewState will persist from POST to POST. It's actually stored inside a hidden field on your form so that it gets POSTed back to your server all the time.

As long as you aren't relying on the Session you shouldn't have any problems rebuilding page state. It's easy to test your Page's state code if you want though: just set your session to expire after 60 seconds in your web.config then load your page, wait a little more than a minute (surf over to Stack Overflow and answer some questions) and then click a button on your page.

Answer 9

Also, as a gotcha, by default ASP.NET encrypts ViewState with an autogenerated key. This can be overridden with the MachineKey element in the web.congif file. Even though ViewState won't expire, it can become invalid if a different autogenerated key is used to decrypt ViewState, such as after an IIS Reset, redeploying an application, or hitting a different server in a web farm. If you're planning on storing viewstate for long periods of time, watch out for how it's encrypted/decrypted.

http://msdn.microsoft.com/en-us/library/ms998288.aspx