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Asked: 2026-05-10T21:00:22+00:00

I am currently receiving this error: Validation of viewstate MAC failed. If this application

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I am currently receiving this error:

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.

I have found multiple solutions to this error. The solution we are currently using is to add a static MachineKey field at the machine level and to use static validation keys and decryption keys. 

<MachineKey validationKey='' decryptionKey='' validation='SHA1' decruption='AES' />

Will this solution work for .NET 3.5? Is there a more elegant solution?

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1 Answer

  1. Is your web app hosted in a webfarm?

    If so, the reason for this is that a page is rendered by server 1, and posted to server 2. Therefore, machine keys are different, and the validation failed.

    It will work on ASP.NET 3.5 as well.

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