The HiddenField control provides you with a way to store information in the page without displaying it. For example, you might store a user-preference setting in a HiddenField control.
To add a HiddenField control to a page
Drag the HiddenField control from the Toolbox task pane to your page.
Because there is no visual representation of a HiddenField control, you won't be able to see it in Design view, but you can see the control in Code view.
To put information into a HiddenField control, you set its Value property to the value you want to store between postbacks.
As with any other web server control, the information in a HiddenField control is available during postback. The information is not persisted outside the page.