如何获取Autofac for WebAPI2的容器？

Question

In Ninject I can get object needed for interface by using class WebContainerManager

Ninject definition:

 var logManager = new LogManagerAdapter(); 
 container.Bind<ILogManager>().ToConstant(logManager); 

Ninject usage:

var log = WebContainerManager.Get<ILogManager>().GetLog(typeof(WebApiApplication));

My question is how to do the same in Autofac, to get needed class for interface?

UPDATE 1: Im using WebAPi 2, not MVC.

Answer 1

You can create your builder.

var builder = new ContainerBuilder();

// Usually you're only interested in exposing the type
// via its interface:
builder.RegisterType<SomeType>().As<IService>();

// However, if you want BOTH services (not as common)
// you can say so:
builder.RegisterType<SomeType>().AsSelf().As<IService>();

Then you will be able to build your IoC:

IContainer Container = builder.Build();

And a simple example of How to get resource from container:

// Create the scope, resolve your IService,
// use it, then dispose of the scope.
using (var scope = Container.BeginLifetimeScope())
{
  var writer = scope.Resolve<IService>();
  writer.DoSomething();
}

Answer 2

If you need access to Autofac container from the class that was resolved by Autofac itself, then you can specify dependency on IComponentContext that is automatically provided by Autofac.

Example:

public void SomeComponent(IComponentContext context)
{
   this.context = context;
}
...
// somewhere inside SomeComponent
context.Resolve<ILogManager>();

If your code is running inside ASP.Net environment, then you most probably set its DependencyResolver, thus you can always access it like:

DependencyResolver.Current.GetService<ILogManager>();

but as it is already mentioned in other comments, Service Locator is an anti-pattern that should be avoided.

In order to integrate autofac container with standard MVC dependency resolution mechanism you need to:

• install Autofac.Mvc5 nuget package

• set DependencyResolver with the following code

  var container = builder.Build(); DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

And in case you don't mind having explicit dependency on Autofac in your application code you can access global Autofac resolver reference the same way you use Ninject WebContainerManager:

var log = AutofacDependencyResolver.Current.Resolve<ILogManager>().GetLog(typeof(WebApiApplication));