ASP.NET Web API 2 with Autofac Owin

Table of Contents

1. Introduction
2. packages.config
3. Startup Class
4. API Controller Class: TestController
5. Interface
6. Class Implementing Interface
7. Autofac Service Module
8. Conclusion

Introduction

This blog shows how to set up Autofac for dependency injection in ASP.NET Web API 2 with Owin.

packages.config

Following is the packages.config. You can use this NuGet command to install all of these to your project: Update-Package -ProjectName MyProject -reinstall

<?xml version="1.0" encoding="utf-8"?>

Startup Class

using Autofac;
using Autofac.Integration.WebApi;
using Microsoft.Owin;
using Owin;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Web;
using System.Web.Compilation;
using System.Web.Http;
using WebApplication2.Controllers;

[assembly: OwinStartup(typeof(WebApplication2.Startup))]
namespace WebApplication2
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            HttpConfiguration config = new HttpConfiguration();
            // register api routing.
            WebApiConfig.Register(config);
            app.UseWebApi(config);

            var builder = new ContainerBuilder();

            var assemblies = BuildManager.GetReferencedAssemblies().Cast().ToArray();

            builder.RegisterAssemblyModules(assemblies);
            builder.RegisterApiControllers(assemblies);

            var container = builder.Build();
            config.DependencyResolver = new AutofacWebApiDependencyResolver(container);

            app.UseAutofacMiddleware(container);
            app.UseAutofacWebApi(config);
            app.UseWebApi(config);
        }
    }
}

API Controller Class: TestController

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;

namespace WebApplication2.Controllers
{
    public class TestController : ApiController
    {
        Interface1 _i;
        public TestController(Interface1 i)
        {
            _i = i;
        }

        public IHttpActionResult Get()
        {

            return Ok(new List() { "Hi", "I", "'m", "Just", "testing" });
        }
    }
}

Interface

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WebApplication2
{
    public interface Interface1
    {
        string Do();
    }
}

Class Implementing Interface

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WebApplication2
{
    public class Class1 : Interface1
    {
        public string Do()
        {
            return Guid.NewGuid().ToString();
        }
    }
}

Autofac Service Module

using Autofac;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WebApplication2
{
    public class ServiceModule : Module
    {
        protected override void Load(ContainerBuilder builder)
        {
            builder.RegisterType().As().InstancePerDependency();
        }
    }
}

Conclusion

With Autofac and Owin, you can easily set up dependency injection in your ASP.NET Web API 2 project. The key steps are configuring the Owin startup class, registering your controllers and services with Autofac, and creating service modules for your dependency bindings.