我们在项目中很早就开始使用autofac，也以为知道与mvc和webapi集成的做法。
var builder = new ContainerBuilder(); // Mvc Register builder.RegisterControllers(Assembly.GetExecutingAssembly()).AsSelf().PropertiesAutowired(); builder.RegisterFilterProvider(); builder.RegisterType<UserService>().As<IUserService>().InstancePerLifetimeScope(); //WebApi Register builder.RegisterApiControllers(Assembly.GetExecutingAssembly()).AsSelf().PropertiesAutowired(); builder.RegisterWebApiFilterProvider(GlobalConfiguration.Configuration); builder.RegisterWebApiModelBinderProvider(); var container = builder.Build(); // Set the dependency resolver for Web API. var webApiResolver = new AutofacWebApiDependencyResolver(container); GlobalConfiguration.Configuration.DependencyResolver = webApiResolver; // Set the dependency resolver for MVC. var resolver = new AutofacDependencyResolver(container); DependencyResolver.SetResolver(resolver);
在实际Controller和ApiController中通过构造函数注入，这不必多说。
但是，在实际项目需求的时候，有些地方不方便使用构造函数，或者说就要使用服务定位IContainer.Resolve(ServiceType)的方式来获得服务的实例。
曾经在项目中看到过有人通过把Container设区全局静态变量来获得对象容器。这个方式在Local的情况下，不会有太大问题。在Mvc中，容器DependencyResolver.Current本身也是通过尽量变量来实现的。
public class DependencyResolver
{
public DependencyResolver();
public static IDependencyResolver Current { get; }
...
}
但是和C端不同的是，Web服务是基于请求的，autofac内部的InstancePerLifetimeScope，InstancePerHttpRequest，InstancePerApiRequest等都是基于每次请求的Scope,而静态的Container明显生命周期不符合。
所以我们写代码的时候都是通过DependencyResolver.Current.GetService()和GlobalConfiguration.Configuration.DependencyResolver.GetService()来分别获取Mvc和WebApi的对象。那么问题来了，我有一段业务逻辑在BLL中，Mvc和WebApi可以都调用到，其中需要Resolve一个服务，那么如何来指定容器呢？
带着问题，我们先来看看DependencyResolver.Current和GlobalConfiguration.Configuration.DependencyResolver，通过一组实验来对比一下：
public class WebApiApplication : System.Web.HttpApplication
{
public static System.Web.Mvc.IDependencyResolver mvcResolver;
public static System.Web.Http.Dependencies.IDependencyResolver apiResolver;
protected void Application_Start()
{
...
builder.RegisterType<UserService>().As<IUserService>().InstancePerLifetimeScope();
// Set the dependency resolver for Web API.
var webApiResolver = new AutofacWebApiDependencyResolver(container);
apiResolver = webApiResolver;
GlobalConfiguration.Configuration.DependencyResolver = webApiResolver;
// Set the dependency resolver for MVC.
var resolver = new AutofacDependencyResolver(container);
mvcResolver = resolver;
DependencyResolver.SetResolver(mvcResolver);
}
}
public interface IUserService
{
}
public class UserService : IUserService
{
}
我们分别定义了两个静态变量mvcResolver和apiResolver来存储两个不同的容器，并注册了一组服务，指定其生命周期为InstancePerLifetimeScope，先看看Mvc的容器
public class HomeController : Controller
{
IUserService _userservice;
public HomeController(IUserService userService)
{
_userservice = userService;
var a = DependencyResolver.Current.GetService<IUserService>();
var b = WebApiApplication.mvcResolver.GetService<IUserService>();
var c1 = ReferenceEquals(userService, a); //true
var c2 = ReferenceEquals(userService, b); //true
var c3 = ReferenceEquals(b, a); //true
}
}
我们在HomeContorller中通过三种不同方法来获取对象，目的是三个对象都应该是同一个对象，结果也符合预期，再看看WebApi的:
public class ValuesController : ApiController
{
IUserService _userservice;
public ValuesController(IUserService userService)
{
_userservice = userService;
var a = GlobalConfiguration.Configuration.DependencyResolver.GetService(typeof(IUserService));
var b = WebApiApplication.apiResolver.GetService(typeof(IUserService));
var c1 = ReferenceEquals(userService, a); //false
var c2 = ReferenceEquals(userService, b); //false
var c3 = ReferenceEquals(b, a); //true
}
}
发现通过GlobalConfiguration.Configuration.DependencyResolver来获取的对象，竟然不等于构造函数解析出来的对象，有点毁三观。说明它并不是当前上下文的对象，也就是说这个对象的生命周期不在控制范围内。
那么Mvc和WebApi可不可以用同一个容器来指定呢？
我们先来看看stackoverflow上的这篇文章：Is it possible to configure Autofac to work with ASP.NET MVC and ASP.NET Web Api
其实Mvc和WebApi分别是两个独立的依赖解析器，这点没什么问题，一个是System.Web.Mvc.IDependencyResolver另一个是System.Web.Http.Dependencies.IDependencyResolver，两个互相不串。
最后，一个很重要的对象来了，那就是Autofac.IComponentContext，它就是解析的上下文，通过它来解析的对象是符合当前上下文的，我们再来看看之前的例子:
public class HomeController : Controller
{
IUserService _userservice;
public HomeController(IUserService userService, IComponentContext com)
{
_userservice = userService;
var a = DependencyResolver.Current.GetService<IUserService>();
var b = WebApiApplication.mvcResolver.GetService<IUserService>();
var d = com.Resolve<IUserService>();
var d1 = ReferenceEquals(userService, d); //true
var c1 = ReferenceEquals(userService, a); //true
var c2 = ReferenceEquals(userService, b); //true
var c3 = ReferenceEquals(b, a); //true
}
}
WebApi：
public class ValuesController : ApiController
{
IUserService _userservice;
public ValuesController(IUserService userService, IComponentContext com)
{
_userservice = userService;
var a = GlobalConfiguration.Configuration.DependencyResolver.GetService(typeof(IUserService));
var b = WebApiApplication.apiResolver.GetService(typeof(IUserService));
var d = com.Resolve<IUserService>();
var d1 = ReferenceEquals(userService, d); //true
var c1 = ReferenceEquals(userService, a); //false
var c2 = ReferenceEquals(userService, b); //false
var c3 = ReferenceEquals(b, a); //true
}
}
