Dependency Injection and Inversion of Control in C#

 Why do we need the Dependency Injection in C#?

The Dependency Injection is a design pattern that allows us to develop loosely coupled software components. In other words, we can say that this design pattern is used to reduce the tight coupling between the software components. As a result, we can easily manage future changes and other complexity in our application.

Before understanding the Dependency Injection Design Pattern using C#, first, we need to understand what is tight coupling and what is loose coupling in software development. So let’s understand these two concepts first.

What is Tight Coupling in Software Design?

Tight coupling means classes and objects are dependent on each other. That means when a class is dependent on another concrete class, then it is said to be a tight coupling between these two classes. In that case, if we change the dependent object, then we also need to change the classes where this dependent object is used. If your application is a small one, then it is not that difficult to handle but if you have a big enterprise-level application, then its really very difficult to handle to make these changes.

What is Loose Coupling in Software Design?

Loosely coupling means two objects are independent of each other. That means if we change one object then it will not affect another object. The loosely coupled nature of software development allows us to manage future changes easily and also allows us to manage the complexity of the application.

What is Dependency Injection Design Pattern in C#?

The Dependency Injection Design Pattern in C# is a process in which we are injecting the object of a class into a class that depends on that object. The Dependency Injection design pattern is the most commonly used design pattern nowadays to remove the dependencies between the objects.

Dependency Injection (DI) is a design pattern used to implement IoC. It allows the creation of dependency objects outside of a class and provides those objects to a class in different ways. Using DI, we move the creation and binding of the dependent objects outside of the class that depends on them. 

Different Types of Dependency Injection in C#?

The injector class injects the dependency object to a class in three different ways. They are as follows.

Constructor Injection: When the Injector injects the dependency object (i.e. service) through the client class constructor, then it is called as Constructor Injection.

Property Injection: When the Injector injects the dependency object (i.e. service) through the public property of the client class, then it is called as Property Injection. This is also called as the Setter Injection.

Method Injection: When the Injector injects the dependency object (i.e. service) through a public method of the client class, then it is called as Method Injection. In this case, the client class implements an interface that declares the method(s) to supply the dependency object and the injector uses this interface to supply the dependency object (i.e. service) to the client class.

Design Principle:

The Design principles are provided with some high-level guidelines or you can say mechanism to make the software designs more understandable, flexible as well as maintainable. They (i.e. Design Principles) do not provide any implementation and also they are not bound to any programming languages. So, you can use design principles irrespective of the programming languages.

Design Pattern:

The Design patterns are reusable solutions to the problems that we encounter in our day to day programming. They are basically used to solve the problems of object generation and integration. For example, if you want to create a class that can have only one instance for the entire application then you can use the Singleton design pattern which ensures that a class has only one instance for the entire application and provides a global point of access to it.

Inversion of Control (IoC):

The main objective of Inversion of control (IoC) is to remove dependencies between the objects of an application which makes the application more decoupled and maintainable.

Understanding the Dependency Inversion Principle:

The dependency Inversion Principle also helps us to achieve loose coupling between the classes. It is highly recommended to use both DIP and IoC together in order to achieve loose coupling between the classes.

The DIP (DIP) states that high-level modules/classes should not depend upon low-level modules/classes. Both should depend upon abstractions. Secondly, abstractions should not depend upon details. Details should depend upon abstractions.

We need to keep the High-level module and Low-level module as loosely coupled as possible. When a class knows about the design and implementation of another class, it raises the risk that if we do any changes to one class will break the other class. So we must keep these high-level and low-level modules/classes loosely coupled as much as possible. To do that, we need to make both of them dependent on abstractions instead of knowing each other.

IoC Container:

The IoC Container is a great framework to create dependencies and inject them automatically whenever required throughout the application so that we as a software programmer don’t have to put additional time and effort into it. It automatically creates the necessary objects based on the request and also automatically injects them whenever required. DI Container helps us to manage dependencies within the application in a straightforward and simple way.

There are different IoC Containers available for .NET such as Unity, Ninject, StructureMap, Autofac, etc. I will discuss more regarding the IoC Container chapter in our upcoming articles.