Called by the ASP.NET page framework to notify server controls that use composition-based implementation to create any child controls they contain in preparation for posting back or rendering.
When you develop a composite or templated server control, you must override this method. Controls that override the Control.CreateChildControls method should implement the System.Web.UI.INamingContainer interface to avoid naming conflicts.
For more information, see ASP.NET Web Server Controls Templates and Developing Custom ASP.NET Server Controls.