<httpModules> <add type="System.Web.Caching.OutputCacheModule" /> <add type="System.Web.SessionState.SessionStateModule" /> <add type="System.Web.Security.WindowsAuthenticationModule" /> <add type="System.Web.Security.FormsAuthenticationModule" /> <add type="System.Web.Security.PassportAuthenticationModule" /> <add type="System.Web.Security.RoleManagerModule" /> <add type="System.Web.Security.UrlAuthorizationModule" /> <add type="System.Web.Security.FileAuthorizationModule" /> <add type="System.Web.Security.AnonymousIdentificationModule" /> <add type="System.Web.Profile.ProfileModule" /> <add type="System.Web.Mobile.ErrorHandlerModule, System.Web.Mobile, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /> <add type="System.ServiceModel.Activation.HttpModule, System.ServiceModel.Activation, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" /> <add type="System.Web.Routing.UrlRoutingModule" /> <add type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/> </httpModules>
大家看到没有，我上面标红的那一行：<add type="System.Web.Routing.UrlRoutingModule" />
UrlRoutingModule并不是MVC特有的，这是一个全局配置，就是说所有的ASP.NET请求都会到达这里，所以该Module还不能最终决定是MVC还是WebForm请求。但是也是至关重要的地方。
（2）通过在全局Web.Config中注册 System.Web.Routing.UrlRoutingModule，IIS请求处理管道接到请求后，就会加载 UrlRoutingModule类型的Init()方法。其源码入下：
[TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")] public class UrlRoutingModule : IHttpModule { // Fields private static readonly object _contextKey = new object(); private static readonly object _requestDataKey = new object(); private RouteCollection _routeCollection; // Methods protected virtual void Dispose() { } protected virtual void Init(HttpApplication application) { if (application.Context.Items[_contextKey] == null) { application.Context.Items[_contextKey] = _contextKey; application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache); } } private void OnApplicationPostResolveRequestCache(object sender, EventArgs e) { HttpApplication application = (HttpApplication) sender; HttpContextBase context = new HttpContextWrapper(application.Context); this.PostResolveRequestCache(context); } [Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")] public virtual void PostMapRequestHandler(HttpContextBase context) { } public virtual void PostResolveRequestCache(HttpContextBase context) { RouteData routeData = this.RouteCollection.GetRouteData(context); if (routeData != null) { IRouteHandler routeHandler = routeData.RouteHandler; if (routeHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0])); } if (!(routeHandler is StopRoutingHandler)) { RequestContext requestContext = new RequestContext(context, routeData); context.Request.RequestContext = requestContext; IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext); if (httpHandler == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[] { routeHandler.GetType() })); } if (httpHandler is UrlAuthFailureHandler) { if (!FormsAuthenticationModule.FormsAuthRequired) { throw new HttpException(0x191, SR.GetString("Assess_Denied_Description3")); } UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this); } else { context.RemapHandler(httpHandler); } } } } [TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] void IHttpModule.Dispose() { this.Dispose(); } [TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] void IHttpModule.Init(HttpApplication application) { this.Init(application); } // Properties public RouteCollection RouteCollection { get { if (this._routeCollection == null) { this._routeCollection = RouteTable.Routes; } return this._routeCollection; } [TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] set { this._routeCollection = value; } } }
看看上面的UrlRoutingModule源码里面是怎么实现Init方法的，Init()方法里面我标注红色的地方：
application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);