Dependency Injection

· Dependency Injection (DI) is a design pattern that implements inversion of control principle for resolving dependencies.

· Instead of hardcoding dependencies within a class, dependencies are “injected” into the class from the outside

· There are three type of Injection

1. Constructor Injection : One of the most common approaches to dependency injection in C# is constructor injection. In this approach, dependencies are provided through a class’s constructor.
 

public class EmployeeService

{

    private readonly IEmployeeRepository _employeeRepository;

    public EmployeeService (IEmployeeRepository employeeRepository)

    {

        _employeeRepository = employeeRepository;

    }

}

Here, the EmployeeService class depends on an interface IEmployeeRepository. The dependency is injected through the constructor, allowing different implementations of IEmployeeRepository to be supplied.

2.  Property Injection : Another approach is property injection, where dependencies are exposed as public properties and are set externally. While this approach offers flexibility, it may make it less clear what dependencies a class requires.

public class EmployeeService

{

    public IEmployeeRepository employeeRepository { get; set; }

}

3. Method Injection : Method injection involves passing dependencies through methods instead of constructors or properties. This approach is useful when a dependency is required for a specific method but not for the entire lifetime of the object.

Public class EmployeeService

{

    public void SetEmployeeRepository(IEmployeeRepository employeeRepository)

    {

        _ employeeRepository = employeeRepository;

    }

}

· The Benefits of Dependency Injection

1. Loose Coupling: Dependency injection promotes loose coupling by removing the direct dependencies between classes.

2. Testability: Injecting mock or test implementations of dependencies, developers can isolate the component under test, making it easier to verify its behavior without external dependencies.

3. Reusability: Dependency injection promotes code reuse.

Dependency injection is a powerful technique that promotes loosely coupled, maintainable, and testable code. By applying dependency injection principles in your C# projects, you can achieve better modularity, reusability, and flexibility.