This method is commonly used when you override the Control.DataBind method when developing templated data-bound server controls. If you do not call this method, child control view–state information can be written to a parent server control, only to be overridden when the data is bound.
When recreating child controls of a System.Web.UI.Control, use the Control.ClearChildViewState method to clear child view state so that it does not get applied to the new controls inadvertently.
For more information about using this method, see How to: Create Templated User Controls.