Dependency Injection in .NET Core

⚙️ How It Works in .NET Core

.NET Core uses a three-step process to implement Dependency Injection (DI):

1. Register Services

You register your services in the Startup.cs file (or Program.cs in .NET 6+), using the IServiceCollection interface.

services.AddTransient<IMyService, MyService>();
services.AddScoped<IMyService, MyService>();
services.AddSingleton<IMyService, MyService>();

• Transient: A new instance is created every time it's requested.
• Scoped: One instance per request.
• Singleton: One instance for the entire application lifetime.

Comparison of Service Lifetimes in .NET Core

Example Registration

services.AddTransient<IMyService, MyService>();
services.AddScoped<IMyService, MyService>();
services.AddSingleton<IMyService, MyService>();
  

Injection Example

public class MyController : Controller
{
    private readonly IMyService _myService;

    public MyController(IMyService myService)
    {
        _myService = myService;
    }
}
  

2. Build the Service Provider

.NET Core automatically builds the service provider when the application starts. This provider resolves dependencies when needed.

3. Inject Dependencies

You inject dependencies into constructors of controllers, services, or other classes:

public class MyController : Controller
{
    private readonly IMyService _myService;

    public MyController(IMyService myService)
    {
        _myService = myService;
    }
}

.NET Core automatically provides the correct implementation based on what you registered.

🧪 Benefits of DI in .NET Core

• Loose Coupling: Classes depend on abstractions, not concrete implementations.
• Testability: Easier to mock dependencies for unit testing.
• Maintainability: Centralized configuration of dependencies.