Agile Principles, Patterns, and Practices in C#

21. COMMAND and ACTIVE OBJECT: Versatility and Multitasking

© Jennifer M. Kohnke

No man has received from nature the right to command his fellow human beings.

—Denis Diderot (1713–1784)

Of all the design patterns that have been described over the years, COMMAND impresses me as one of the simplest and most elegant. But we shall see, the simplicity is deceptive. The range of uses that COMMAND may be put to is probably without bound.

The simplicity of COMMAND, as shown in Figure 21-1, is almost laughable. Listing 21-1 doesn’t do much to dampen the levity. It seems absurd that we can have a pattern that consists of nothing more than an interface ...