أساسيات حاوية DI

var builder = WebApplication.CreateBuilder(args);

// Register services
builder.Services.AddScoped<IUserRepository, UserRepository>();
builder.Services.AddScoped<UserService>();

var app = builder.Build();
app.Run();

public interface IUserRepository
{
    User? GetById(int id);
}

public class UserRepository : IUserRepository
{
    public User? GetById(int id)
    {
        // fetch from database
        return new User { Id = id, Name = "Alice" };
    }
}

public class UserService
{
    private readonly IUserRepository _repo;

    public UserService(IUserRepository repo)
    {
        _repo = repo;
    }

    public User? FindUser(int id) => _repo.GetById(id);
}

builder.Services.AddSingleton<IConfig, AppConfig>();
builder.Services.AddScoped<IUserRepository, UserRepository>();
builder.Services.AddTransient<IEmailService, SmtpEmailService>();
builder.Services.AddScoped<UserService>();

// Anti-pattern (service locator) — use sparingly
public class ManualResolver
{
    private readonly IServiceProvider _sp;

    public ManualResolver(IServiceProvider sp) => _sp = sp;

    public void DoWork()
    {
        var svc = _sp.GetRequiredService<UserService>();
        svc.FindUser(1);
    }
}

builder.Services.AddScoped(typeof(IRepository<>), typeof(Repository<>));

// Resolves as:
// IRepository<User> -> Repository<User>
// IRepository<Order> -> Repository<Order>

builder.Services.AddScoped<IMyService, MyService>();

// Detect scope violations at startup
builder.Host.UseDefaultServiceProvider(options =>
{
    options.ValidateScopes = true;
    options.ValidateOnBuild = true;
});

builder.Services.AddScoped<IUserRepository, UserRepository>();

// Decorator pattern
builder.Services.Decorate<IUserRepository, CachedUserRepository>();
// Requires Scrutor NuGet package

app.MapGet("/users/{id}", (int id, UserService svc) =>
{
    var user = svc.FindUser(id);
    return user is null ? Results.NotFound() : Results.Ok(user);
});