Use the Enabled property to turn the Timer control on and off. When you set Enabled to true, the Timer control starts its timer countdown when the Web page is rendered.
On postback, you can change property values in the Enabled property, and the changes will be reflected when the Web page content is rendered in the browser. If you change the Enabled property and then change it back to its original value during the same postback, the Timer control runs as if no change had been made.