Asp.net Validation of viewstate MAC failed

Question

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

 Sys.WebForms.PageRequestManagerServerErrorException: 
 Validation of viewstate MAC f         


        

Answer 1

I had this problem, and for me the answer was different than the other answers to this question.

I have an application with a lot of customers. I catch all error in the application_error in global.asax and I send myself an email with the error detail. After I published a new version of my apps, I began receiving a lot of Validation of viewstate MAC failed error message.

After a day of searching I realized that I have a timer in my apps, that refresh an update panel every minute. So when I published a new version of my apps, and some customer have left her computer open on my website. I receive an error message every time that the timer refresh because the actual viewstate does not match with the new one. I received this message until all customers closed the website or refresh their browser to get the new version.

I'm sorry for my English, and I know that my case is very specific, but if it can help someone to save a day, I think that it is a good thing.