Beginning in a recent OS Patch, you can no longer disable the ViewState MAC check.  Microsoft says this is because using this is a security risk and they know better than you. While that may be true, there are many cases where application may not be able to avoid a ViewStateMAC error. And so Microsoft's decision to FORCE you to use it can adversely affect your application. One example is an application that dynamically adds fields to a form based on database settings. An administrator decides to remove a field from a form while a user has the form open in a browser. The field is removed and then the user submits his form to the server. The application attempts to rebuild the form but now with one less field and guess what happens! The user is rewarded with a ViewState error. I have a client where this is now occurring after the server OS was patched.
I personally do not appreciate Microsoft forcing us to use security feature...it simply should be our choice. Reg ...

Go to the complete details ...