The types in the System.Web.UI.Design.WebControls namespace extend Visual Studio's design-time support for creating web controls. Most types in this namespace are designers that provide special design-time-specific HTML (which may be only slightly different than runtime HTML) and custom System.Drawing.Design.UITypeEditor classes that provide the graphic interface for modifying some special properties. The most detailed implementations of these features can be found in the types used for the System.Web.UI.WebControls.DataGrid and System.Web.UI.WebControls.DataList controls, such as DataGridComponentEditor and DataGridDesigner. These classes provide sophisticated property builders that offer complete design-time customization in a multipage "applet."
These designers, UI type editors, and component editors have no effect on the runtime capabilities of a control. They are also not used directly in code. That means that the System.Web.UI.Design.WebControls namespace is probably of most interest to developers who are interested in creating controls and add-ins of their own and want to review Microsoft's examples. Unfortunately, while you can review the interfaces these types have and extend them in your own code, the implementation details are not provided. Usually, it makes most sense to create control designers that inherit from the base System.Web.UI.Design.ControlDesigner class.
Figures Figure 38-1 and Figure 38-2 show the types in this namespace.