C# Dependency Injection

Dependency Injection Concept

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• Dependency Injection is a method where a class does not directly create dependent objects, but receives necessary objects (dependencies) from the outside.
• This reduces code coupling and significantly improves reusability and testability.

Main Injection Methods

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• Constructor Injection
  Receiving necessary dependencies through the constructor at the time of object creation. This is the most recommended DI method.
• Property/Setter Injection
  Injecting dependencies through public properties (setters, or methods). Mainly used for optional dependencies.
• Interface Injection
  Injecting dependencies by forcing an object to implement a specific interface. This is not widely used directly in C#.

Practical Example

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// Constructor Injection Example
public class UserService
{
    private readonly ILogger _logger;
    public UserService(ILogger logger)
    {
        _logger = logger;
    }
    public void DoSomething()
    {
        _logger.Log("Work has been processed.");
    }
}

Utilization in ASP.NET Core

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• .NET and ASP.NET Core have built-in DI containers, enabling easy dependency injection in layered structures such as Services and Repositories.
• Service Lifetime settings are available through AddTransient, AddScoped, and AddSingleton methods, each with different instance creation rules.

Summary of Advantages

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• Reduced coupling, high flexibility
• Easy to write test code, facilitates modularization
• Automated object lifecycle management

In C#, DI has established itself as an essential pattern when considering maintainability, scalability, and testing convenience.

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Dependency injection in ASP.NET Core

Learn how ASP.NET Core implements dependency injection and how to use it.