ASP.NET view state is the technique used by an ASP.NET Web page to persist
changes to the state of a Web Form across postbacks.That is when a form is submitted in ASP .NET, the form reappears in the browser window together with all form values.
The ViewState indicates the status of the page when submitted to the server. The status is defined through a hidden field placed on each page with a <form runat=”server”> control.
Hidden field placed on each page would be something as this
< input type=”hidden” name=”__VIEWSTATE” value=”CEbzzzEnmmz+Bc8IDFlnpgCLJ/HB00.” >
Maintaining the ViewState is the default setting for ASP.NET Web Forms. If you want to NOT maintain the ViewState, include the directive l%@ Page EnableViewState=”false” %> at the top of an .aspx page or add the attribute EnableViewState=”false” to any control.