6.5 Summary

Inheritance is crucially important to the .NET Framework in general and to Windows Forms in particular. All visual classes must inherit from the Control class either directly or indirectly. Inheritance is a powerful technique that lets us incorporate the full implementation of a base class into our own controls, but it is a double-edged sword.

It is helpful that all controls and all containers are based on a single implementation provided by the Control class. This greatly increases the chances of successful interoperation between controls. But inheritance is a complex relationship, and it is very difficult to define a good base class. Most base classes only become truly reusable as a result of multiple design iterations based on experience gained by attempts to derive from them. If the base and derived classes are under common ownership, this is less of a problem. The base class can be modified on demand as shortcomings in its design are identified, and the author of the derived class is less likely to make false assumptions about how the base class works when deriving from it. But it is wise to be wary of inheriting from a class you do not control unless that class has been work- hardened through refactoring driven by experience.