How To Fix the: “Validation of viewstate MAC failed” Error (ASP.NET MVC)

Backup from

http://adam.kahtava.com/journal/2009/11/23/how-to-fix-the-validation-of-viewstate-mac-failed-error-aspnet-mvc/

The “Validation of viewstate MAC failed” error only occurred when a page contained an HTML form element that made use of MVC’s AntiForgeryToken. The quick fix was to delete my __RequestVerificationToken cookie, but the error would rear its ugly head the minute I touched my assemblies. The long term solution was to add a machineKey element to my Web.config file - asking visitors to delete a specific cookies when visiting my site was not a viable option.

How I fixed the “Validation of viewstate MAC failed” error on Shared Hosting:

1. I used the Generator Tool to generate a machine key
2. I added the machineKey element to my Web.config file

My Web.config now looks similar to this:

Anyhow, I hope this post helps anyone else that’s encountering this error.