Configure Dependency Injection for .NET Core with Lamar

Dependency Injection

Dependency injection (DI) is a software design pattern, which is a technique for achieving Inversion of Control (IoC) between classes and their dependencies.

Lamar

A fast IoC container heavily optimized for usage within ASP.Net Core and other .Net server-side applications. The successor to the venerable StructureMap library, the original IoC tool for .Net.

Steps to configure Lamar for a .NET Core solution

1. Go to Program.cs and add UseLamar() in the CreateHostBuilder method.

   public static IHostBuilder CreateHostBuilder(string[] args)
   {
       return Host.CreateDefaultBuilder(args)
           .UseLamar() //Add this line
           .ConfigureWebHostDefaults(webBuilder =>
           {
               webBuilder.UseStartup<Startup>();
           });
   }

2. Add an interface named IInstaller, to be used for configuring various services for your solution.

   using Lamar;
   using Microsoft.Extensions.Configuration;
   
   namespace Project.Web.Installers
   {
       internal interface IInstaller
       {
           void InstallServices(ServiceRegistry services, IConfiguration configuration);
       }
   }

3. Add a class named InstallerExtensions with the below code.

   using Lamar;
   using Microsoft.Extensions.Configuration;
   using System;
   using System.Collections.Generic;
   using System.Linq;
   
   namespace Project.Web.Installers
   {
       public static class InstallerExtensions
       {
           public static void InstallServicesInAssembly(this ServiceRegistry services, IConfiguration configuration)
           {
               List<IInstaller> installers = typeof(Startup).Assembly.ExportedTypes.Where(x =>
                   typeof(IInstaller).IsAssignableFrom(x) && !x.IsInterface && !x.IsAbstract).Select(Activator.CreateInstance).Cast<IInstaller>().ToList();
   
               installers.ForEach(installer => installer.InstallServices(services, configuration));
           }
       }
   }
   

4. Go to Startup.cs and add the ConfigureContainer method to the class.

   public void ConfigureContainer(ServiceRegistry services)
   {
       services.InstallServicesInAssembly(Configuration);
   
       // for Lamar IOC, add all assemblies for the project but ignore Test assemblies
       services.Scan(s =>
       {
           s.AssembliesFromApplicationBaseDirectory(assembly =>
           assembly.GetName().Name.Contains("Project", StringComparison.OrdinalIgnoreCase) &&
           !assembly.GetName().Name.Contains("Tests", StringComparison.OrdinalIgnoreCase));
           s.WithDefaultConventions();
       });
   }

5. To inject a service, you can now create Installer files for each service. Below is an example.

   namespace Project.Web.Installers
   {
       public class ApiServiceInstaller : IInstaller
       {
           public void InstallServices(ServiceRegistry services, IConfiguration configuration)
           {
               //Load IApiService in DI
               services.AddSingleton<IApiService, ApiService>();
           }
       }
   }

This convention can be used to set up plugin services for your solution as well. I will be using this configuration for the next of my articles over .NET Core.

Please drop a comment below if you have any queries.