Earlier, we discussed the dependency injection pattern, which states that all dependencies, such as the repositories and view models, must be passed through the constructor of the class. This has several benefits:
- It increases the readability of the code since we can quickly determine all the external dependencies.
- It makes dependency injection possible.
- It makes unit testing possible by mocking classes.
- We can control the life time of an object by specifying whether it should be a singleton or a new instance for each resolution.
Dependency injection is a pattern that lets us determine, at runtime, which instance of an object should be passed to a constructor when an object is created. We do this by defining a container where we register all the types of a class. We let the framework that we are using resolve any dependencies between them. Let's say that we ask the container for a MainView class. The container takes care of resolving MainViewModel and any dependencies that the class has.
To set this up, we need to reference a library called Autofac. There are other options out there, so feel free to switch to one that better fits your needs. We also need an entry point to resolve the types into instances. To do this, we will define a bare-bones Resolver class. To wrap it all up, we need a bootstrapper that we will call to initialize the dependency injection configuration.
