title: Why clear controls in CreateChildControls
body: <p>All of the examples of ASP.NET composite controls always clear child controls as the first action within CreateChildControls. Why is this? As I understand it this method is always called via EnsureChildControls which sets a flag to indicate that it has already been called and thus does not call CreateChildControls again.</p>
  
  <p>Is CreateChildControls called by other aspects of the infrastructure? If so under what circumstances?</p>