viewstate error

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G

Guest

Hi

Users seem to be getting the following intermitent error whe they post a
form.

Validation of viewstate MAC failed. If this application is hosted by a
Web Farm or cluster, ensure that <machineKey> configuration specifies
the same validationKey and validation algorithm. AutoGenerate cannot be
used in a cluster.

We are not in a cluster situation. I believe it may be because there is a
delay in posting back so the viewstate is expiring. I wanted to know if there
is any way to increase the timeout of the view state, is it bound to the
session timeout (we are not using forms authentication)?

Alternatively any way to turn this viewstate check off (it is a restriced
admin site so there should be no security problems although I would prefer
just to extend the timeout)
 
ViewState does not timeout. It is an encrypted string in your page (hidden
field). There is a setting on the @Page directive for ViewStateMac. Set it
both ways (forget which setting cures this, but a google might solve it).
The second thing to do is generate your keys. You can find machineKey
generators on the web.

--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA
http://gregorybeamer.spaces.live.com

*************************************************
Think outside of the box!
*************************************************
 
Hi

Thanks for your reply, I think I was not being that clear, I am aware view
state itself does not time out as such but according to what I read "
ASP.NET will perform a simple digest on the viewstate and check it later
when page postback, however, this digest is not valid forever"

Also would setting the key make any difference in a non-cluster environment.

Scott
 
There's a web.config key that you can set to enable or disable the ViewStateMac
setting.

In your <pages> tag, add enableViewStateMac="true" or enableViewStateMac="false".

-dl
 
Hello Scott,

As for the ViewState validation error you encountered, there does exists
some issue that will result to the behavior. One is hosting web applicaiton
in webfarm environment which cause request send to different server (with
different machinekey) raise viewstate validation error. Another problem is
as you said, the ViewStateMac(enabled by default) is a randomly generated
digest value and it is not expected to work forever, and that's why
sometimes the server will also raise such error when use pickup a url from
the webcrawler's search result cache(which contains invalid viewstate
content).

So far, the ASP.NET's ViewState setting only provide the
"EnableViewStateMac" and "viewStateEncryptionMode" two configuration
options, and the "viewStateEncryptionMode" is specific to viewstate
encryption which is not used normally. As for ViewStateMac, we can only
control whether to enable it, but can not control the valid lifecycle of
the generated MAC value(it is internally fixed). BTW, since the error
will raise occasionally when the user postback a form after a long period
idle, do you think it possible that you embed some client-script in your
certain page (which need such protetion) and automatically postback the
form after a certain long period? Thus, if the user hasn't perform any
action on the form for a long time, the page will postback itself to make
its states refresh. Also, you can disable ViewStatemac for the certain
pages, however, there will still raise server-side exception when the
ViewState is corrupted.

Please feel free to post here if you have any other ideas or questions.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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Hi

Thanks for your reply, does the sentence "Also, you can disable ViewStatemac
for the certain pages, however, there will still raise server-side exception
when the
ViewState is corrupted." mean that changing the ViewStatemac setting even in
the web.config will not necessarily fix the problem?



Scott
 
Thanks for your reply Scott,

Yes, IMO "turn off ViewStateMac" is not the way to fix the problem. This is
because if we turn off the ViewStateMac check, when a problem page (with
invalid viewstate) postback, the server-side will not verify the viewstate
since MAC is turned off, however, when the page framework parse the
viewstate, it will encounter problem which will raise some unexpected error
and this will be more ambiguous than a ViewState validation error. Do you
think so?

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead


This posting is provided "AS IS" with no warranties, and confers no rights.
 
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