The ASP.NET ViewState is a representation of the state of a page when it was last processed on the server. The
ViewState information is stored by default...
1 ...on the server in a Session variable that is unique for each page.
2 ...in a hidden form element as plain text.
3 ...in a hidden form element as a Base64 encoded string.
4 ...in a hidden form element that is encrypted so it cannot be tampered with.