Technically, there isn't an enormous difference between the composition and derivation approaches for building custom activities. When we built our
GetUploadActivity earlier, the new activity did derive from the
SequenceActivity class. Composition and derivation both use inheritance. Many of the topics we'll cover in this section we could also apply to
Derivation versus composition is more a state of mind. In composition, we focus on arranging child activities inside a custom activity, and we build bigger activities
from smaller activities. With derivation, we focus on designing a single activity—its properties and execution model. The derivation approach is often the low‑level approach. Let's build a custom activity ...