Viewstate verification failed. Reason: The viewstate supplied failed integrity check

Question

It's been a while that I'm getting "Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster." error on GridView post-backs.

I've defined the same machine-keys on my sites but I (sometimes) get the message.

Any clue?

Answer 1

Add this to your web.config file in the system.web section:

<machinekey validationkey="xxx" decryptionkey="xxx" validation="SHA1" decryption="AES" />

Provide your own validation and decryption keys ("xxx" above),

which you can try to generated from here

Please do refer this microsoft kb