Notes to Inheritors:
When control state is saved, a string object is returned to the client as a variable that is stored in an HTML HIDDEN element. Override this method to extract the state information to use in your control.
Control state is intended for small amounts of critical data, such as a page index or a keyword. Using control state for large amounts of data can adversely affect page performance. For more information, see ASP.NET State Management.
The following code example overrides the SaveControlState method in a custom ASP.NET control. When this method is invoked, it determines whether the internal property currentIndex is set to a non-default value and, if so, saves the value to control state.
The OnInit method is overridden to call the RegisterRequiresControlState method on the Page to indicate that the custom control uses control state.