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In software engineering, dependency injection is a design pattern in which an object or function receives other objects or functions that it depends on. A form of inversion of control, dependency injection aims to separate the concerns of constructing objects and using them, leading to loosely coupled programs.
AddTransient() - This method creates a Transient service. A new instance of a Transient service is created each time it is requested. AddScoped() - This method creates a Scoped service. A new instance of a Scoped service is created once per request within the scope.
Dependency Injection (DI) is a design pattern used to implement IoC. It allows the creation of dependent objects outside of a class and provides those objects to a class through different ways. Using DI, we move the creation and binding of the dependent objects outside of the class that depends on them.
Start here.
Also see A-beginners-guide-to-Dependency-Injection. (Obsolete)
Elsewhere on SO:
What is the purpose of DI?
The purpose of Dependency Injection is to reduce coupling in your application to make it more flexible and easier to test.
How does it benefit?
Objects don't have hard coded dependencies. If you need to change the implementation of a dependency, all you have to do is Inject a different type of Object.
How does it implemented?
There are various methods of Dependency Injection. Check out the Wikipedia article to see examples of each. Once you understand those, you can start investigating the various Dependency Injection frameworks.
Very short,
What is the purpose of DI? With dependency injection, objects don't define their dependencies themselves, the dependencies are injected to them as needed.
How does it benefit ? The objects don't need to know where and how to get their dependencies, which results in loose coupling between objects, which makes them a lot easier to test.
How is it implemented ? Usually a container manages the lifecycle of objects and their dependencies based on a configuration file or annotations.
Try taking a look at: http://martinfowler.com/articles/injection.html
DI allows us to swap out components, improve testability and ensure that components are loosely coupled. DI allows to resolve dependencies at run time using DI containers such as Windsor Castle, Unity, Spring.net, MEF which allows applications to be extensible.
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