解决Autofac MVC 自动注入在 Areas拆分到不同dll下的注入失败问题

由于项目业务复杂，创建了多个Areas 并把他们放在了不同的项目中，项目使用AutoFac做的IOC

配置代码为

public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
//依赖注入
var builder = new ContainerBuilder();
builder.RegisterModule(new ConfigurationSettingsReader("autofac"));
builder.RegisterControllers(Assembly.GetExecutingAssembly());

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

AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
}
}

namespace xxx.Web.Person.Controllers
{
/// <summary>
/// 定位模块
/// </summary>
public class LocationController : Controller
{
private ILocationService _location;
public LocationController(ILocationService location)
{
_location = location;
}
}
}

[MissingMethodException: 没有为该对象定义无参数的构造函数。]
System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98
System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241
System.Activator.CreateInstance(Type type, Boolean nonPublic) +69
System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +67

[InvalidOperationException: 尝试创建“xxx.Web.Person.Controllers.HomeController”类型的控制器时出错。请确保控制器具有无参数公共构造函数。]

通过错误信息得知 AutoFac 的RegisterControllers 只是 注入了xxx.Web的 Controllers 对于引用的 xxx.web.Person.dll 下的 Controller 没有注入。
解决方法如下：

public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
//依赖注入
var builder = new ContainerBuilder();
builder.RegisterModule(new ConfigurationSettingsReader("autofac"));
builder.RegisterControllers(Assembly.GetExecutingAssembly());

//解决Areas在不同的Dll中注入问题
var assemblies = new DirectoryInfo(
HttpContext.Current.Server.MapPath("~/bin/"))
.GetFiles("*.dll")
.Select(r => Assembly.LoadFrom(r.FullName)).ToArray();
builder.RegisterAssemblyTypes(assemblies)
.Where(r => r.BaseType == typeof(Controller))
.InstancePerHttpRequest();

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

AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
}
}