ViewState persist the values of controls of particular page in the client (browser) when post back operation done. When user requests another page previous page data no longer available.

SessionState persist the data of particular user in the server. This data available till user close the browser or session time completes.

Phani Krishna Reddy V

Unlike Session state ViewState is a property of the web controls.

Both are used to persist certain data.

Values stored in the session are available across different pages in an application.

Where as the vdata contained in a control is persisted between page's post back by using that controls ViewState property.

View state cannot be used if the page donot post back to itself.