The Control.ClearChildControlState method is used when child control-state information written to the parent control's control state is overridden as new child controls are created, such as when data-binding child controls in a templated data-bound server control. Calling the Control.ClearChildControlState method to empty child controls before calling the Control.SaveControlState method reduces the size of the control-state information that must be stored or transmitted.
When recreating child controls of a System.Web.UI.Control object, use the Control.ClearChildControlState method to clear child control state so that it does not get applied to the new controls inadvertently.
To clear both the child control state and view state, use the Control.ClearChildState method.