在ControllerBuilder类中设置ControllerFactory，然后使用ControllerFactory创建Controller。 http请求在进入httphandler映射处理时，通过ControllerBuilder的Current获取ControllerFactory，然后使用默认或者注册的（如果注册地话）ControllerFactory创建controller。默认的工厂是一个DefaultControllerFactory对象,由下面代码可以看出。
internal ControllerBuilder(IResolver<IControllerFactory> serviceResolver)
{
ControllerBuilder controllerBuilder = this;
IResolver<IControllerFactory> resolver = serviceResolver;
if (resolver == null)
resolver = (IResolver<IControllerFactory>) new SingleServiceResolver<IControllerFactory>((Func<IControllerFactory>) (() => this._factoryThunk()),(IControllerFactory) new DefaultControllerFactory()
{
ControllerBuilder = this
}, "ControllerBuilder.GetControllerFactory");
controllerBuilder._serviceResolver = resolver;
}
而Controller的产生是通过DefaultControllerFactory的CreateController来实现的，代码如下：
public virtual IController CreateController(RequestContext requestContext, string controllerName)
{
if (requestContext == null)
throw new ArgumentNullException("requestContext");
if (string.IsNullOrEmpty(controllerName))
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");
Type controllerType = this.GetControllerType(requestContext, controllerName);
return this.GetControllerInstance(requestContext, controllerType);
}
然后查看GetControllerType方法：
protected internal virtual Type GetControllerType(RequestContext requestContext, string controllerName)
{
if (string.IsNullOrEmpty(controllerName))
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");
object obj;
if (requestContext != null && requestContext.RouteData.DataTokens.TryGetValue("Namespaces", out obj))
{
IEnumerable<string> enumerable = obj as IEnumerable<string>;
if (enumerable != null && Enumerable.Any<string>(enumerable))
{
HashSet<string> namespaces = new HashSet<string>(enumerable, (IEqualityComparer<string>) StringComparer.OrdinalIgnoreCase);
Type withinNamespaces = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, namespaces);
if (withinNamespaces != (Type) null || false.Equals(requestContext.RouteData.DataTokens["UseNamespaceFallback"]))
return withinNamespaces;
}
}
if (this.ControllerBuilder.DefaultNamespaces.Count > 0)
{
HashSet<string> namespaces = new HashSet<string>((IEnumerable<string>) this.ControllerBuilder.DefaultNamespaces, (IEqualityComparer<string>) StringComparer.OrdinalIgnoreCase);
Type withinNamespaces = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, namespaces);
if (withinNamespaces != (Type) null)
return withinNamespaces;
}
return this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, (HashSet<string>) null);
}
可以看到最终都归结到同一个方法GetControllerTypeWithinNamespaces中，代码如下：
private Type GetControllerTypeWithinNamespaces(RouteBase route, string controllerName, HashSet<string> namespaces)
{
this.ControllerTypeCache.EnsureInitialized(this.BuildManager);
ICollection<Type> controllerTypes = this.ControllerTypeCache.GetControllerTypes(controllerName, namespaces);
switch (controllerTypes.Count)
{
case 0:
return (Type) null;
case 1:
return Enumerable.First<Type>((IEnumerable<Type>) controllerTypes);
default:
throw DefaultControllerFactory.CreateAmbiguousControllerException(route, controllerName, controllerTypes);
}
}
而方法EnsureInitialized()是通过IBuildManager获取程序中所有实现了IController的类型，然后在这些类型里用路由数据或者ControllerBuilder中的命名空间和controller的名称进行匹配，如果没有匹配，返回null，如果有一个匹配，返回，如果有多个，抛出异常！
现在获取到了controllerType的类型，然后返回到工厂的CreateController的最后一步，查看GetControllerInstance方法,代码如下：
protected internal virtual IController GetControllerInstance(RequestContext requestContext, Type controllerType)
{
if (controllerType == (Type) null)
{
throw new HttpException(404, string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_NoControllerFound, new object[1]
{
(object) requestContext.HttpContext.Request.Path
}));
}
else
{
if (typeof (IController).IsAssignableFrom(controllerType))
return this.ControllerActivator.Create(requestContext, controllerType);
throw new ArgumentException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_TypeDoesNotSubclassControllerBase, new object[1]
{
(object) controllerType
}), "controllerType");
}
}
可以看到，这个时候又使用到了另外一个对象ControllerActivator，由DefaultControllerFactory的构造函数可以看出
internal DefaultControllerFactory(IControllerActivator controllerActivator, IResolver<IControllerActivator> activatorResolver, IDependencyResolver dependencyResolver)
{
if (controllerActivator != null)
this._controllerActivator = controllerActivator;
else
this._activatorResolver = activatorResolver ?? (IResolver<IControllerActivator>) new SingleServiceResolver<IControllerActivator>((Func<IControllerActivator>) (() => (IControllerActivator) null),(IControllerActivator) new DefaultControllerFactory.DefaultControllerActivator(dependencyResolver), "DefaultControllerFactory constructor");
}
默认使用的是实现了接口IResolver<TService>的SingleServiceResolver<TService>对象默认注册的一个内部对象DefaultControllerActivator，然后调用它的create方法,代码如下：
public IController Create(RequestContext requestContext, Type controllerType)
{
try
{
return (IController) (this._resolverThunk().GetService(controllerType) ?? Activator.CreateInstance(controllerType));
}
catch (Exception ex)
{
throw new InvalidOperationException(string.Format((IFormatProvider) CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_ErrorCreatingController, new object[1]
{
(object) controllerType
}), ex);
}
}
而DefaultControllerActivator对象中的属性_resolverThunk是一个Func<IDependencyResolver> _resolverThunk委托对象，我们通过DefaultControllerFactory构造函数中调用的new DefaultControllerFactory.DefaultControllerActivator(dependencyResolver)，可以看到DefaultControllerActivator的构造函数
public DefaultControllerActivator(IDependencyResolver resolver)
{
if (resolver == null)
this._resolverThunk = (Func<IDependencyResolver>) (() => DependencyResolver.Current);
else
this._resolverThunk = (Func<IDependencyResolver>) (() => resolver);
}
对它的设置，如果在自己实现的ControllerFactory的构造函数中传递了自己定义的一个IDependencyResolver对象或者DependencyResolver的SetResolver方法设置了一个自定义的IDependencyResolver对象，就会使用它，如果没有，则使用默认的DependencyResolver.Current,可以看到DependencyResolver.Current是一个实现了IDependencyResolver接口对象的引用，从他的构造函数
public DependencyResolver()
{
this.InnerSetResolver((IDependencyResolver) new DependencyResolver.DefaultDependencyResolver());
}
看出它使用的是一个内部私有的对象DefaultDependencyResolver，
private class DefaultDependencyResolver : IDependencyResolver
{
public object GetService(Type serviceType)
{
if (!serviceType.IsInterface)
{
if (!serviceType.IsAbstract)
{
try
{
return Activator.CreateInstance(serviceType);
}
catch
{
return (object) null;
}
}
}
return (object) null;
}
public IEnumerable<object> GetServices(Type serviceType)
{
return Enumerable.Empty<object>();
}
}
它的GetService方法，通过反射创建了我们需要的controller对象，由此，controller创建成功！
Area中controller的解析过程：
首先我们知道，在程序刚启动时，我们会调用AreaRegistration.RegisterAllAreas()方法：
internal static void RegisterAllAreas(RouteCollection routes, IBuildManager buildManager, object state)
{
foreach (Type type in TypeCacheUtil.GetFilteredTypesFromAssemblies("MVC-AreaRegistrationTypeCache.xml", new Predicate<Type>(AreaRegistration.IsAreaRegistrationType), buildManager))
((AreaRegistration) Activator.CreateInstance(type)).CreateContextAndRegister(routes, state);
}
它是先查找出程序中所有实现了AreaRegistration的区域对象，然后创建他们的实例，调用实例的CreateContextAndRegister方法，来创建AreaRegistrationContext对象，
internal void CreateContextAndRegister(RouteCollection routes, object state)
{
AreaRegistrationContext context = new AreaRegistrationContext(this.AreaName, routes, state);
string @namespace = this.GetType().Namespace;
if (@namespace != null)
context.Namespaces.Add(@namespace + ".*");
this.RegisterArea(context);
}
然后调用RegisterArea方法，对路由进行注册，可以看出，这个时候还做了一个额外的事情，就是给上下文的属性Namespaces添加了一个以（区域注册对象所在命名空间+".*")的命名空间，这个最后会用于解析controller对象，通过后续代码可以看出，这个上下文的Namespaces会被使用。
而一般的RegisterArea方法就是通过我们自己创建的区域注册对象来重写实现的，是通过调用AreaRegistrationContext对象的MapRoute()方法来实现路由注册的.
public Route MapRoute(string name, string url, object defaults, object constraints, string[] namespaces)
{
if (namespaces == null && this.Namespaces != null)
namespaces = Enumerable.ToArray<string>((IEnumerable<string>) this.Namespaces);
Route route = RouteCollectionExtensions.MapRoute(this.Routes, name, url, defaults, constraints, namespaces);
route.DataTokens["area"] = (object) this.AreaName;
bool flag = namespaces == null || namespaces.Length == 0;
route.DataTokens["UseNamespaceFallback"] = (object) (bool) (flag ? 1 : 0);
return route;
}
这个方法中我们看到如果注册路由时没有指定命名空间，则会把上下文的Namespaces属性拿来使用，除了注册路由之外，这个方法还做了一步工作，在路由数据的DataTokens中添加了一个以UseNamespaceFallback为key的数据，它的值是通过判断如果注册路由的命名空间参数和上下文的Namespaces都为空的情况下，为1，否则为0；为1，则在解析controller时需要使用controllerBuilder中的DefaultNamespaces属性的值中的命名空间。这个逻辑我们可以再DefaultControllerFactory的GetControllerType()方法中可以看到！
而且我们可以看到路由数据RouteData中表示区域的area的值是存在DataTokens属性中
