CQRS-CleanInstallers

A clean way to implement dependency injection(DI) in startup.cs on .Net Core Web Project with CQRS & MediatR.

---

Web Project had configured with few of layered class libiary project, swagger installation for the API documentaion and CORS for resource sharing.

startup.cs - before clean installers

// This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            /** Application layer & Infrastructure layer DI reference */
            services.AddApplication();
            services.AddInfrastructure();

            /** Swagger reference */
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "CQRS With MediatR APIs", Version = "v1" });
            });

            /** CORS reference */
            services.AddCors(options =>
            {
                options.AddPolicy(name: "MyAllowSpecificOrigins",
                                  builder =>
                                  {
                                      builder.AllowAnyOrigin()
                                             .AllowAnyHeader()
                                             .AllowAnyMethod();
                                  });
            });
        }

startup.cs - after clean installers

// This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.InstallServicesInAssembly(Configuration);
        }

steps

1. Create a folder(named as: Installers) in the API layer
2. Create an interface

 public interface IInstaller
 {
    void InstallServices(IServiceCollection services, IConfiguration configuration);
 }

3. Create respective DI classes and inherit IInstaller interface
4. DI

   public class DIInstaller : IInstaller
   {
       public void InstallServices(IServiceCollection services, IConfiguration configuration)
       {
           services.AddControllers();
   
           services.AddApplication();
           services.AddInfrastructure();
       }
   }
   

5. Swagger

   public class SwaggerInstaller : IInstaller
   {
       public void InstallServices(IServiceCollection services, IConfiguration configuration)
       {
           services.AddSwaggerGen(c =>
           {
               c.SwaggerDoc("v1", new OpenApiInfo { Title = "CQRS With MediatR APIs", Version = "v1" });
           });
       }
   }
   

6. CORS

   public class CorsInstaller : IInstaller
   {
       public void InstallServices(IServiceCollection services, IConfiguration configuration)
       {
           services.AddCors(options =>
           {
               options.AddPolicy(name: "MyAllowSpecificOrigins",
                                 builder =>
                                 {
                                     builder.AllowAnyOrigin()
                                            .AllowAnyHeader()
                                            .AllowAnyMethod();
                                 });
           });
       }
   }
   

7. Create a class that extends Microsoft.Extensions.DependencyInjection

   public static class InstallerExtensions
   {
       public static void InstallServicesInAssembly(this IServiceCollection services, IConfiguration configuration)
       {
           typeof(Startup).Assembly.ExportedTypes
               .Where(x => typeof(IInstaller).IsAssignableFrom(x) && !x.IsInterface && !x.IsAbstract)
               .Select(Activator.CreateInstance).Cast<IInstaller>()
               .ToList()
               .ForEach(installer => installer.InstallServices(services, configuration));
       }
   }
   

8. In startup.cs under services section clean the existing code and include below mentioned code

   services.InstallServicesInAssembly(Configuration);
   

Thats it, clean DI configuration was finished. similarly we can configure other DI(s) or we can extend existing DI(s).

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