ASP.NET MVC 4 Dependency Injection - ablealias/MVC GitHub Wiki

In Object Oriented Programming paradigm, objects work together in a collaboration model where there are contributors and consumers. Naturally, this communication model generates dependencies between objects and components, becoming difficult to manage when complexity increases.

The Dependency Injection pattern is a particular implementation of Inversion of Control. Inversion of Control (IoC) means that objects do not create other objects on which they rely to do their work. Instead, they get the objects that they need from an outside source (for example, an xml configuration file).

Dependency Injection (DI) means that this is done without the object intervention, usually by a framework component that passes constructor parameters and set properties.

The Dependency Injection (DI) Design Pattern

At a high level, the goal of Dependency Injection is that a client class (e.g. the golfer) needs something that satisfies an interface (e.g. IClub). It doesn't care what the concrete type is (e.g. WoodClub, IronClub, WedgeClub or PutterClub), it wants someone else to handle that, the dependency resolver (e.g. a good caddy). The Dependency Resolver in ASP.NET MVC can allow you to register your dependency logic somewhere else (e.g. a container or a bag of clubs).

The advantages of using Dependency Injection pattern and Inversion of Control are the following:

• Reduces class coupling
• Increases code reusing
• Improves code maintainability
• Improves application testing