Asp.net Validation of viewstate MAC failed

asp.net viewstate machinekey
Arbelac picture Arbelac · Apr 30, 2011 · Viewed 152.7k times · Source

I am receiving the following error at certain times on asp.net website.

 Sys.WebForms.PageRequestManagerServerErrorException: 
 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.

When page refresh goes,no problem.How can I solve this problem?

Answer

mBotros picture mBotros · Apr 30, 2011

If you're using a web farm and running the same application on multiple computers, you need to define the machine key explicitly in the machine.config file:

<machineKey validationKey="JFDSGOIEURTJKTREKOIRUWTKLRJTKUROIUFLKSIOSUGOIFDS..." decryptionKey="KAJDFOIAUOILKER534095U43098435H43OI5098479854" validation="SHA1" />

Put it under the <system.web> tag.

The AutoGenerate for the machine code can not be used. To generate your own machineKey see this powershell script: https://support.microsoft.com/en-us/kb/2915218#bookmark-appendixa

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