I am using the SessionPageStatePersister class with a history size of 9 to keep viewstate in the user's session. I have a problem where sometimes, when the user posts back, the viewstate appears to be missing.
I am not using any popup dialog/windows or frames. The user doesn't think they are pressing the back button. Bascially, I can't find any reason why the viewstate would be missing. One clue is that the user feels like it happens most when they haven't used the page in a while. Of course, the most immediate answer would seem to be their session ended and of course, their viewstate would be lost then too. However, I have tested that scenario (expired session) and the code behaves properly by redirecting the user to the login page. Additionally, the user claims he is still logged in (still has session) when this happens and that he can click a button and the page then behaves correctly which indicates it is finding the proper ...
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