Delegates vs. Interfaces

Delegates are useful when:

• A single method is being called.
• A class may want to have multiple implementations of the method specification.
• It is desirable to allow using a static method to implement the specification.
• An event-like design pattern is desired (for more information, see the Events Tutorial).
• The caller has no need to know or obtain the object that the method is defined on.
• The provider of the implementation wants to "hand out" the implementation of the specification to only a few select components.
• Easy composition is desired.

Interfaces are useful when:

• The specification defines a set of related methods that will be called.
• A class typically implements the specification only once.
• The caller of the interface wants to cast to or from the interface type to obtain other interfaces or classes.