Improve built-in ASP.NET Core DI container with Scrutor

ASP.NET Core has built-in dependency injection (DI) container. It’s easy and simple for the smaller project where you register all your dependencies (e.g. services, repositories, e.t.c.) by hand. Microsoft.Extensions.DependencyInjection has not built-in type scanning functionality, so if your project will grow, using it can be pretty hard. But you can resolve this problem by using Scrutor. Scrutor is an extension for built-in DI that allows you scan assembly and decorate services. In this article, we will look at scanning functionality.

Problem: You want to register all classes from the specific assembly (e.g. all repositories).

To resolve this problem in an efficient way, you need to install Scrutor to your project (NuGet Package).

Package Manager Console

Install-Package Scrutor

When you have successfully installed Scrutor you can use it by invoking method Scan on the IServiceCollection collection in the ConfigureServices method.

services.Scan(scan => scan
     .FromCallingAssembly()
     .AddClasses(classes => classes.InNamespaces("SampleWebAppScrutor.Repositories"))
     .AsImplementedInterfaces()
     .WithTransientLifetime()
);

Let’s dive into this example:

FromCallingAssembly - scan the calling assembly
AddClasses - get classes only from namespace SampleWebAppScrutor.Repositories
AsImplementedInterfaces - specify what type you want to register these classes are
WithTransientLifetime - specify the lifetime of registrations

So instead of registering your service by hand like this:

services.AddTransient<IUserRepository, UserRepository>();
services.AddTransient<ICustomerRepository, CustomerRepository>();
services.AddTransient<I...Repository, ...Repository>();

you can write code that will register all repositories in your project without the need of specifying them by hand in ConfigureServices method.

In the GitHub you can find a sample project: https://github.com/kmatyaszek/SampleWebAppScrutor

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