How to decode viewstate

Question

I need to see the contents of the viewstate of an asp.net page. I looked for a viewstate decoder, found Fridz Onion\'s ViewState Decoder but it asks for the url of a page to

Answer 1

Normally, ViewState should be decryptable if you have the machine-key, right? After all, ASP.net needs to decrypt it, and that is certainly not a black box.