Object-oriented programming in C# part 2

Abstraction

"Abstraction - is the process of separating ideas from specific instances of those ideas" (Wikipedia)

Key ideas of abstraction:

• ignore irrelevant features, properties and methods
• emphasizing on really important features
• keep only those details about an object that are relevant to the current perspective

Abstraction goals

• simplify complex representation and expose only important properties of an object
• build simplified model of an object
• hide unimportant properties of an object

Abstraction in C#

Abstraction in C# might be achieved in several ways:

• with Interfaces
• with abstract classes
• with inheritance

Cohesion

Cohesion describes how closely all the methods in a class support a central purpose of the class

Good module should have high (or strong) cohesion

Cohesion is high (or strong) if:

• methods carry out a small number of related activities
• classes aimed for single purpose
• advantages of high cohesion:
• reduced module complexity
• increased system maintainability
• increased module reusability

Coupling

Coupling describes how tightly a classes or modules are related to other classes or modules

Good class or method should have low (loose) coupling:

• modules should have a very little dependency on other modules
• a module must be easily re-used by other modules (avoid direct dependencies among modules)