Dependency Injection

Demo application for my presentation on Dependency Injection at CoderCamp 18 in Hamilton, ON.

The presentation is available here.

Terms

• Dependency Inversion – A design principal that high level modules should not depend on low level modules, but both should depend on abstractions
• Inversion of Control – A design pattern where objects are coupled at run-time rather than compile time
• Dependency Injection – One form of IoC where functionality is passed into an object through constructors or parameters

Advantages

• Makes adapting to changing requirements easier
• Makes unit testing much easier
• New functionality can be plugged in
• Applications can be composed from smaller modules
• Promotes loose coupling between modules

Disadvantages

• Code can be hard to follow
• Run-time errors instead of compile-time errors
• Programming to the least common denominator
• Possible performance issues

Useful Links

• Martin Fowler’s paper on the Dependency Inversion Principle
• Castle Windsor
• StructureMap
• Spring.net
• Autofac
• Unity
• Ninject
• Funq