Question

can we access viewstate and session objects at unload event of page.

Answer 1

The "unload" event is called as soon as the page response has been sent to the client browser, there’s usually nothing useful you can do in this event, other than clear up resources (i.e. file/database handles, etc).

Unload is called after the page has been fully rendered, sent to the client, and is ready to be discarded. At this point, page properties such as Response and Request are unloaded and any cleanup is performed.

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During the unload stage, the page and its controls have been rendered, so you cannot make further changes to the response stream. If you attempt to call a method such as the Response.Write method, the page will throw an exception. (From ASP.NET Page Life Cycle Overview).

You might possibly be able to read viewstate, you certainly can’t change it, and the same propbably holds true for session. What are you trying to achieve?