If you are experiening this error “The Security validation for this page is invalid.Click back in your web browser, refresh the page, and try your operation again” , even though you have impersonate user as System Account.
No problem, you got to tell the web application that you will be doing some impersonate tricks inside your code. To do this
go to the Central Administration site–> Under Application management, Click Manage web application.
Select the web application you are working on, in the ribbon Click General Settings, scroll down to see the Web Page Security Validation, turn off the Security validation–> save the settings.
The error has gone now 🙂