Dependency Injection in .NET Core

.NET Core has a built-in dependency injection (DI) container used to wire up services at startup.

Composition root: The place where object graphs are composed — typically Program.cs / Startup.

builder.Services.AddScoped<IOrderRepository, OrderRepository>();
builder.Services.AddScoped<IEmailSender, SmtpEmailSender>();

Lifetimes: Singleton, Scoped, Transient — choose based on state and thread-safety.

Architecture impact: Proper DI usage enforces boundaries, enables testing, and keeps infrastructure swappable.

Reference:

Microsoft: Dependency Injection in .NET

https://learn.microsoft.com/aspnet/core/fundamentals/dependency-injection