Scrutor the built-in Dependency Injection (DI)

By Tareq Marji -

 

Scrutor is a lightweight .NET library that extends the built-in Dependency Injection (DI) system in ASP.NET Core (or any .NET application that uses Microsoft.Extensions.DependencyInjection) by providing assembly scanning and automatic registration of services.

Key Features of Scrutor

  1. Assembly Scanning
    Automatically registers services by scanning assemblies instead of manually specifying each one. This is helpful in large applications or when following clean architecture or DDD patterns.
  2. Service Registration by Convention
    You can register services based on naming conventions or interface implementation. For example, register all classes that implement a specific interface.
  3. Decorators
    Scrutor supports applying the decorator pattern easily through DI, allowing you to wrap services (e.g., for logging, validation, etc.) without modifying the core implementation.

 

Example Usage

1. Basic Scanning and Registration

csharp

CopyEdit

services.Scan(scan => scan

    .FromAssemblyOf<ISomeService>() // or FromCallingAssembly()

    .AddClasses(classes => classes.AssignableTo<ISomeService>())

    .AsImplementedInterfaces()

    .WithScopedLifetime());

This code:

  • Scans the assembly containing ISomeService
  • Finds all classes that implement ISomeService
  • Registers them with their implemented interfaces
  • Sets the lifetime to Scoped

 

2. Using Decorators

csharp

CopyEdit

services.AddScoped<IService, Service>();

services.Decorate<IService, ServiceDecorator>();

This means:

  • IService is first implemented by Service
  • Then it's wrapped by ServiceDecorator (which takes an IService in its constructor)

Why Use Scrutor?

  • Cleaner Code: Reduces boilerplate code in Startup.cs or Program.cs
  • Better Organization: Encourages organizing services by convention and interface
  • Advanced Scenarios: Supports decorators, filtering, and more powerful DI patterns

 

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