HiddenField Class
Represents a hidden field used to store a non-displayed value.
Introduction
The HiddenField control is used to store a value that needs to be persisted across posts to the server. It is rendered as an <input type= "hidden"/>
element.
Normally view state, session state, and cookies are used to maintain the state of a Web Forms page. However, if these methods are disabled or are not available, you can use the HiddenField control to store state values.
To specify the value for a HiddenField control, use the Value property. You can provide a routine that gets called every time the value of the HiddenField control changes between posts to the server by creating an event handler for the ValueChanged event.