This look at composite style controls wraps up ASP.NET's custom control story. Composite controls are a great way to package UI functionality into manageable chunks. Custom composite controls and User controls both maintain internal lists of controls and render them on demand. However, custom composite controls live entirely within an assembly, whereas User controls are split between ASCX files and a backing source code file and/or assembly.
In the next chapter, we'll take a look at some of the other more extensive controls available within ASP.NET.