你真的熟悉ASP.NET MVC的整个生命周期吗？
一、介绍
我们做开发的，尤其是做微软技术栈的，有一个方向是跳不过去的，那就是MVC开发。我相信大家，做ASP.NET MVC 开发有的有很长时间，当然，也有刚进入这个行业的。无论如何，如果有人问你，你知道ASP.NET MVC的生命周期吗？你知道它的来世今生吗？你知道它和 ASP.NET WEBFORM 有什么区别吗?估计，这些问题，有很多人会答不上来，或者说不清楚。今天，我就把我的理解写出来，也是对我自己学习的一次回顾和总结吧。当然，由于本人能力有限，在写的过程中也可能会有一些错误，希望大家多多包涵，当然，更希望大家能不灵赐教，我们共同进步。
在开始之前，我们先来说说，ASP.NET Web Form 和 Asp.net MVC 有什么区别，这里说的区别，当然是本质区别，不是适用语法那个层次的。其实，说起来，ASP.NET WEB FORM 和 ASP.NET MVC 它们两个没有本质区别，使用的都是ASP.NET WEB FORM 的管道处理模型，ASP.NET MVC 也是通过扩展 IHttpModule 和 IHttpHandler 来实现的，都是基于 ASP.NET 的 HttpApplication 的管道处理模型扩展的，在这个层面来说，它们是一样的。当然，大家不要抬杠，我说的本质区别都是在这个方面，不同意的勿喷。
有人会问，ASP.NET MVC 和 ASP.NET WEBAPI 它们会有什么不同吗？好像 WebAPi 能做的，WebMVC都可以完成，第一眼看上去，好像是这样，但是它们有着本质的不同。WebAPI 的处理管道是重新写过的，不是基于 HTTPApplication 管道扩展的。ASP.NET WEB API 类似专人做专事，它的管道处理模型更高效，并且有了 Restfull 的概念。当然，大家如何向了解更细的内容，就需要看源码了。或再说回来，到了 NET CORE 时代，二者又融合管道了。
二、MVC生命周期详述
1、我们既然要说 ASP.NET MVC的生命周期，为了给大家一个整体印象，俗话说，文不如图，我就贴一张图，按着箭头走，相信大家也会不能理解。
2、上图很简单，大家按着箭头走，也能理解的差不多。以下是按着我的理解，划分了4个模块。
（1）、路由模块
RouteBase 是对路由规则的抽象，也就是说，一个 RouteBase 对象，也就代表了一个条 路由规则。在 ASP.NET MVC 中，有一个唯一的子类实现就是 Route ，它同样也是路由规则的代表。我们有了路由规则，一定会把这个规则存放在一个地方，这个地方保存了很多路由规则，这个地方就是 RouteCollection，中文叫“路由集合”，因为这个集合里面包含的就是 RouteBase 对象。
RouteCollection 就是路由集合，用于保存路由规则对象，它的定义形式：
1 [TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
2 public class RouteCollection : Collection<RouteBase>
3 {
4 private class ReadLockDisposable : IDisposable
5 {
6 private ReaderWriterLockSlim _rwLock;
7
8 public ReadLockDisposable(ReaderWriterLockSlim rwLock)
9 {
10 this._rwLock = rwLock;
11 }
12
13 void IDisposable.Dispose()
14 {
15 this._rwLock.ExitReadLock();
16 }
17 }
18 ......
RouteTable 就是路由表，其实它和 RouteCollection 是一样的。
1 public class RouteTable
2 {
3 private static RouteCollection _instance = new RouteCollection();
4
5 public static RouteCollection Routes
6 {
7 get
8 {
9 return RouteTable._instance;
10 }
11 }
12 }
在ASP.NET MVC处理管线中的第一站就是路由模块。当请求到达路由模块后，ASP.NET MVC 框架就会根据 RouteTable 中配置的路由模板来匹配当前请求以获得对应的 Controller 和 Action 信息。具体的匹配过程就是有UrlRoutingModule(System.Web.Routing.UrlRoutingModule)来实现的。如果遇到一个匹配的规则，就会立刻跳出下面的配置。也就是说，配置过程是有顺序的，如果有一个匹配，后面就算有匹配的也不会执行的。
1 namespace System.Web.Routing
2 {
3 [TypeForwardedFrom("System.Web.Routing, Version=3.5.0.0, Culture=Neutral, PublicKeyToken=31bf3856ad364e35")]
4 public class UrlRoutingModule : IHttpModule
5 {
6 private static readonly object _contextKey = new object();
7
8 private static readonly object _requestDataKey = new object();
9
10 private RouteCollection _routeCollection;
11
12 public RouteCollection RouteCollection
13 {
14 get
15 {
16 if (this._routeCollection == null)
17 {
18 this._routeCollection = RouteTable.Routes;
19 }
20 return this._routeCollection;
21 }
22 set
23 {
24 this._routeCollection = value;
25 }
26 }
27
28 protected virtual void Dispose()
29 {
30 }
31
32 protected virtual void Init(HttpApplication application)
33 {
34 if (application.Context.Items[UrlRoutingModule._contextKey] != null)
35 {
36 return;
37 }
38 application.Context.Items[UrlRoutingModule._contextKey] = UrlRoutingModule._contextKey;
39 application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);
40 }
41
42 private void OnApplicationPostResolveRequestCache(object sender, EventArgs e)
43 {
44 HttpApplication httpApplication = (HttpApplication)sender;
45 HttpContextBase context = new HttpContextWrapper(httpApplication.Context);
46 this.PostResolveRequestCache(context);
47 }
48
49 [Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")]
50 public virtual void PostMapRequestHandler(HttpContextBase context)
51 {
52 }
53
54 public virtual void PostResolveRequestCache(HttpContextBase context)
55 {
56 RouteData routeData = this.RouteCollection.GetRouteData(context); 第一步匹配路由规则
57 if (routeData == null)
58 {
59 return;
60 }
61 IRouteHandler routeHandler = routeData.RouteHandler; 第二步：如有匹配，就找到RouteHandler对象，该类型的实例是：MvcRouteHandler。
62 if (routeHandler == null)
63 {
64 throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
65 }
66 if (routeHandler is StopRoutingHandler)
67 {
68 return;
69 }
70 RequestContext requestContext = new RequestContext(context, routeData);
71 context.Request.RequestContext = requestContext;
72 IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);第三步，根据 RouteHandler 对象，找到最终处理请求的 IHttpHandler 的对象，该类型是 MvcHandler
73 if (httpHandler == null)
74 {
75 throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[]
76 {
77 routeHandler.GetType()
78 }));
79 }
80 if (!(httpHandler is UrlAuthFailureHandler))
81 {
82 context.RemapHandler(httpHandler);第四步，有找到的 IHttpHandler 处理请求。
83 return;
84 }
85 if (FormsAuthenticationModule.FormsAuthRequired)
86 {
87 UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
88 return;
89 }
90 throw new HttpException(401, SR.GetString("Assess_Denied_Description3"));
91 }
92
93 void IHttpModule.Dispose()
94 {
95 this.Dispose();
96 }
97
98 void IHttpModule.Init(HttpApplication application)
99 {
100 this.Init(application);
101 }
102 }
103 }
（2）、Controller 创建模块
经过了路由模块，生成了 RouteData 路由数据，它包含了根据路由规则匹配的 Controller 和 Action。有了路由数据，需要有处理器来处理请求，这个任务就交给了 RouteData 的 RouteHandler 属性，它的类型是 IRouteHandler，它的值就是MvcRouteHandler，MvcRouteHandler 调用 GetHttpHandler 获取处理请求的 IHttpHandler 对象，在 MVC 框架中就是 MvcHandler，详细代码如下：
1 namespace System.Web.Mvc
2 {
3 /// <summary>Selects the controller that will handle an HTTP request.</summary>
4 public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState
5 {
6 private struct ProcessRequestState
7 {
8 internal IAsyncController AsyncController;
9
10 internal IControllerFactory Factory;
11
12 internal RequestContext RequestContext;
13
14 internal void ReleaseController()
15 {
16 this.Factory.ReleaseController(this.AsyncController);
17 }
18 }
19
20 [CompilerGenerated]
21 [Serializable]
22 private sealed class <>c
23 {
24 public static readonly MvcHandler.<>c <>9 = new MvcHandler.<>c();
25
26 public static BeginInvokeDelegate<MvcHandler.ProcessRequestState> <>9__20_0;
27
28 public static EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> <>9__20_1;
29
30 public static Func<KeyValuePair<string, object>, bool> <>9__26_0;
31
32 internal IAsyncResult <BeginProcessRequest>b__20_0(AsyncCallback asyncCallback, object asyncState, MvcHandler.ProcessRequestState innerState)
33 {
34 IAsyncResult result;
35 try
36 {
37 result = innerState.AsyncController.BeginExecute(innerState.RequestContext, asyncCallback, asyncState);
38 }
39 catch
40 {
41 innerState.ReleaseController();
42 throw;
43 }
44 return result;
45 }
46
47 internal void <BeginProcessRequest>b__20_1(IAsyncResult asyncResult, MvcHandler.ProcessRequestState innerState)
48 {
49 try
50 {
51 innerState.AsyncController.EndExecute(asyncResult);
52 }
53 finally
54 {
55 innerState.ReleaseController();
56 }
57 }
58
59 internal bool <RemoveOptionalRoutingParameters>b__26_0(KeyValuePair<string, object> entry)
60 {
61 return entry.Value == UrlParameter.Optional;
62 }
63 }
64
65 private static readonly object _processRequestTag = new object();
66
67 internal static readonly string MvcVersion = MvcHandler.GetMvcVersionString();
68
69 /// <summary>Contains the header name of the ASP.NET MVC version.</summary>
70 public static readonly string MvcVersionHeaderName = "X-AspNetMvc-Version";
71
72 private ControllerBuilder _controllerBuilder;
73
74 internal ControllerBuilder ControllerBuilder
75 {
76 get
77 {
78 if (this._controllerBuilder == null)
79 {
80 this._controllerBuilder = ControllerBuilder.Current;
81 }
82 return this._controllerBuilder;
83 }
84 set
85 {
86 this._controllerBuilder = value;
87 }
88 }
89
90 /// <summary>Gets or sets a value that indicates whether the MVC response header is disabled.</summary>
91 /// <returns>true if the MVC response header is disabled; otherwise, false.</returns>
92 public static bool DisableMvcResponseHeader
93 {
94 get;
95 set;
96 }
97
98 /// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary>
99 /// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns>
100 protected virtual bool IsReusable
101 {
102 get
103 {
104 return false;
105 }
106 }
107
108 /// <summary>Gets the request context.</summary>
109 /// <returns>The request context.</returns>
110 public RequestContext RequestContext
111 {
112 get;
113 private set;
114 }
115
116 /// <summary>Gets a value that indicates whether another request can use the <see cref="T:System.Web.IHttpHandler" /> instance.</summary>
117 /// <returns>true if the <see cref="T:System.Web.IHttpHandler" /> instance is reusable; otherwise, false.</returns>
118 bool IHttpHandler.IsReusable
119 {
120 get
121 {
122 return this.IsReusable;
123 }
124 }
125
126 /// <summary>Initializes a new instance of the <see cref="T:System.Web.Mvc.MvcHandler" /> class.</summary>
127 /// <param name="requestContext">The request context.</param>
128 /// <exception cref="T:System.ArgumentNullException">The <paramref name="requestContext" /> parameter is null.</exception>
129 public MvcHandler(RequestContext requestContext)
130 {
131 if (requestContext == null)
132 {
133 throw new ArgumentNullException("requestContext");
134 }
135 this.RequestContext = requestContext;
136 }
137
138 /// <summary>Adds the version header by using the specified HTTP context.</summary>
139 /// <param name="httpContext">The HTTP context.</param>
140 protected internal virtual void AddVersionHeader(HttpContextBase httpContext)
141 {
142 if (!MvcHandler.DisableMvcResponseHeader)
143 {
144 httpContext.Response.AppendHeader(MvcHandler.MvcVersionHeaderName, MvcHandler.MvcVersion);
145 }
146 }
147
148 /// <summary>Called by ASP.NET to begin asynchronous request processing.</summary>
149 /// <returns>The status of the asynchronous call.</returns>
150 /// <param name="httpContext">The HTTP context.</param>
151 /// <param name="callback">The asynchronous callback method.</param>
152 /// <param name="state">The state of the asynchronous object.</param>
153 protected virtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state)
154 {
155 HttpContextBase httpContext2 = new HttpContextWrapper(httpContext);
156 return this.BeginProcessRequest(httpContext2, callback, state);
157 }
158
159 /// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary>
160 /// <returns>The status of the asynchronous call.</returns>
161 /// <param name="httpContext">The HTTP context.</param>
162 /// <param name="callback">The asynchronous callback method.</param>
163 /// <param name="state">The state of the asynchronous object.</param>
164 protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state)
165 {
166 IController controller;
167 IControllerFactory factory;
168 this.ProcessRequestInit(httpContext, out controller, out factory);
169 IAsyncController asyncController = controller as IAsyncController;
170 if (asyncController != null)
171 {
172 BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0;
173 if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null)
174 {
175 arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0));
176 }
177 BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0;
178 EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0;
179 if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null)
180 {
181 arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1));
182 }
183 EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0;
184 MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState
185 {
186 AsyncController = asyncController,
187 Factory = factory,
188 RequestContext = this.RequestContext
189 };
190 SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext();
191 return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext);
192 }
193 Action action = delegate
194 {
195 try
196 {
197 controller.Execute(this.RequestContext);
198 }
199 finally
200 {
201 factory.ReleaseController(controller);
202 }
203 };
204 return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag);
205 }
206
207 /// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary>
208 /// <param name="asyncResult">The asynchronous result.</param>
209 protected internal virtual void EndProcessRequest(IAsyncResult asyncResult)
210 {
211 AsyncResultWrapper.End(asyncResult, MvcHandler._processRequestTag);
212 }
213
214 private static string GetMvcVersionString()
215 {
216 return new AssemblyName(typeof(MvcHandler).Assembly.FullName).Version.ToString(2);
217 }
218
219 /// <summary>Processes the request by using the specified HTTP request context.</summary>
220 /// <param name="httpContext">The HTTP context.</param>
221 protected virtual void ProcessRequest(HttpContext httpContext)
222 {
223 HttpContextBase httpContext2 = new HttpContextWrapper(httpContext);
224 this.ProcessRequest(httpContext2);
225 }
226
227 /// <summary>Processes the request by using the specified base HTTP request context.</summary>
228 /// <param name="httpContext">The HTTP context.</param>
229 protected internal virtual void ProcessRequest(HttpContextBase httpContext)
230 {
231 IController controller;
232 IControllerFactory controllerFactory;
233 this.ProcessRequestInit(httpContext, out controller, out controllerFactory);
234 try
235 {
236 controller.Execute(this.RequestContext);
237 }
238 finally
239 {
240 controllerFactory.ReleaseController(controller);
241 }
242 }
243
244 private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
245 {
246 HttpContext current = HttpContext.Current;
247 if (current != null)
248 {
249 bool? flag = ValidationUtility.IsValidationEnabled(current);
250 bool flag2 = true;
251 if (flag.GetValueOrDefault() == flag2 & flag.HasValue)
252 {
253 ValidationUtility.EnableDynamicValidation(current);
254 }
255 }
256 this.AddVersionHeader(httpContext);
257 this.RemoveOptionalRoutingParameters();
258 string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
259 factory = this.ControllerBuilder.GetControllerFactory();
260 controller = factory.CreateController(this.RequestContext, requiredString);
261 if (controller == null)
262 {
263 throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[]
264 {
265 factory.GetType(),
266 requiredString
267 }));
268 }
269 }
270
271 private void RemoveOptionalRoutingParameters()
272 {
273 IDictionary<string, object> arg_2F_0 = this.RequestContext.RouteData.Values;
274 Func<KeyValuePair<string, object>, bool> arg_2F_1;
275 if ((arg_2F_1 = MvcHandler.<>c.<>9__26_0) == null)
276 {
277 arg_2F_1 = (MvcHandler.<>c.<>9__26_0 = new Func<KeyValuePair<string, object>, bool>(MvcHandler.<>c.<>9.<RemoveOptionalRoutingParameters>b__26_0));
278 }
279 arg_2F_0.RemoveFromDictionary(arg_2F_1);
280 }
281
282 /// <summary>Enables processing of HTTP Web requests by a custom HTTP handler that implements the <see cref="T:System.Web.IHttpHandler" /> interface.</summary>
283 /// <param name="httpContext">An <see cref="T:System.Web.HttpContext" /> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) that are used to service HTTP requests.</param>
284 void IHttpHandler.ProcessRequest(HttpContext httpContext)
285 {
286 this.ProcessRequest(httpContext);
287 }
288
289 /// <summary>Called by ASP.NET to begin asynchronous request processing using the base HTTP context.</summary>
290 /// <returns>The status of the asynchronous call.</returns>
291 /// <param name="context">The HTTP context.</param>
292 /// <param name="cb">The asynchronous callback method.</param>
293 /// <param name="extraData">The data.</param>
294 IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
295 {
296 return this.BeginProcessRequest(context, cb, extraData);
297 }
298
299 /// <summary>Called by ASP.NET when asynchronous request processing has ended.</summary>
300 /// <param name="result">The asynchronous result.</param>
301 void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
302 {
303 this.EndProcessRequest(result);
304 }
305 }
306 }
HttpRuntime 调用 IHttpHandler 类型的调用 ProcessRequest() 方法，用于处理请求。
1 protected internal virtual void ProcessRequest(HttpContextBase httpContext)
2 {
3 IController controller;
4 IControllerFactory controllerFactory;
5 this.ProcessRequestInit(httpContext, out controller, out controllerFactory);创建 IControllerFactory，并创建 IController 对象。
6 try
7 {
8 controller.Execute(this.RequestContext);执行Controller，背后就是调用相应的 Action 方法。
9 }
10 finally
11 {
12 controllerFactory.ReleaseController(controller);
13 }
14 }
核心处理请求的方法是ProcessRequestInit()，用于创建 IController 和 IControllerFactory 实例。IControllerFactory 的实际类型是：DefaultControllerFactory，该类型用于创建 IController 类型的实例。
1 private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
2 {
3 HttpContext current = HttpContext.Current;
4 if (current != null)
5 {
6 bool? flag = ValidationUtility.IsValidationEnabled(current);
7 bool flag2 = true;
8 if (flag.GetValueOrDefault() == flag2 & flag.HasValue)
9 {
10 ValidationUtility.EnableDynamicValidation(current);
11 }
12 }
13 this.AddVersionHeader(httpContext);
14 this.RemoveOptionalRoutingParameters();
15 string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
16 factory = this.ControllerBuilder.GetControllerFactory();
17 controller = factory.CreateController(this.RequestContext, requiredString);
18 if (controller == null)
19 {
20 throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.ControllerBuilder_FactoryReturnedNull, new object[]
21 {
22 factory.GetType(),
23 requiredString
24 }));
25 }
26 }
以上加红的代码就是创建 IController 的实例的逻辑。IController 实例创建完成后，判断是否实现了 IAsyncController 接口，如果是，就异步执行 Controller 方法的调用，否则就同步执行。
1 protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state)
2 {
3 IController controller;
4 IControllerFactory factory;
5 this.ProcessRequestInit(httpContext, out controller, out factory);
6 IAsyncController asyncController = controller as IAsyncController; 判读是否是需要异步执行
7 if (asyncController != null)异步执行
8 {
9 BeginInvokeDelegate<MvcHandler.ProcessRequestState> arg_51_0;
10 if ((arg_51_0 = MvcHandler.<>c.<>9__20_0) == null)
11 {
12 arg_51_0 = (MvcHandler.<>c.<>9__20_0 = new BeginInvokeDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_0));
13 }
14 BeginInvokeDelegate<MvcHandler.ProcessRequestState> beginDelegate = arg_51_0;
15 EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> arg_71_0;
16 if ((arg_71_0 = MvcHandler.<>c.<>9__20_1) == null)
17 {
18 arg_71_0 = (MvcHandler.<>c.<>9__20_1 = new EndInvokeVoidDelegate<MvcHandler.ProcessRequestState>(MvcHandler.<>c.<>9.<BeginProcessRequest>b__20_1));
19 }
20 EndInvokeVoidDelegate<MvcHandler.ProcessRequestState> endDelegate = arg_71_0;
21 MvcHandler.ProcessRequestState invokeState = new MvcHandler.ProcessRequestState
22 {
23 AsyncController = asyncController,
24 Factory = factory,
25 RequestContext = this.RequestContext
26 };
27 SynchronizationContext synchronizationContext = SynchronizationContextUtil.GetSynchronizationContext();
28 return AsyncResultWrapper.Begin<MvcHandler.ProcessRequestState>(callback, state, beginDelegate, endDelegate, invokeState, MvcHandler._processRequestTag, -1, synchronizationContext);
29 }
30 Action action = delegate//同步执行。
31 {
32 try
33 {
34 controller.Execute(this.RequestContext);
35 }
36 finally
37 {
38 factory.ReleaseController(controller);
39 }
40 };
41 return AsyncResultWrapper.BeginSynchronous(callback, state, action, MvcHandler._processRequestTag);
42 }
（3）、Action 执行模块，通过 ControllerActionInvoker 调用 InvokeAction() 执行其方法。Action 方法的执行也有2个版本，一个是异步版本，一个是同步版本。由于 ActionInvoker 实现了 IAsyncActionInvoker 接口，所以也是以已方式执行。该类型是 AsyncControllerActionInvoker。
A、当Controller对象被创建之后，紧接着就会执行Controler 对象的 Execute()，其实背后就是调用 InvokeAction() 方法：
1 public virtual bool InvokeAction(ControllerContext controllerContext, string actionName)
2 {
3 if (controllerContext == null)
4 {
5 throw new ArgumentNullException("controllerContext");
6 }
7 if (string.IsNullOrEmpty(actionName) && !controllerContext.RouteData.HasDirectRouteMatch())
8 {
9 throw new ArgumentException(MvcResources.Common_NullOrEmpty, "actionName");
10 }
11 ControllerDescriptor controllerDescriptor = this.GetControllerDescriptor(controllerContext);
12 ActionDescriptor actionDescriptor = this.FindAction(controllerContext, controllerDescriptor, actionName);
13 if (actionDescriptor != null)
14 {
15 FilterInfo filters = this.GetFilters(controllerContext, actionDescriptor); 获取所有过滤器，全局的、控制器的和方法的
16 try
17 {
18 AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);认证过滤器的执行。
19 if (authenticationContext.Result != null)
20 {
21 AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result);
22 this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result);
23 }
24 else
25 {
26 AuthorizationContext authorizationContext = this.InvokeAuthorizationFilters(controllerContext, filters.AuthorizationFilters, actionDescriptor);授权过滤器的执行。
27 if (authorizationContext.Result != null)
28 {
29 AuthenticationChallengeContext authenticationChallengeContext2 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authorizationContext.Result);
30 this.InvokeActionResult(controllerContext, authenticationChallengeContext2.Result ?? authorizationContext.Result);
31 }
32 else
33 {
34 if (controllerContext.Controller.ValidateRequest)
35 {
36 ControllerActionInvoker.ValidateRequest(controllerContext);
37 }
38 IDictionary<string, object> parameterValues = this.GetParameterValues(controllerContext, actionDescriptor); 获取方法执行参数。
39 ActionExecutedContext actionExecutedContext = this.InvokeActionMethodWithFilters(controllerContext, filters.ActionFilters, actionDescriptor, parameterValues); 执行action，同时执行执行方法前后的 IAcctionFilter
40 AuthenticationChallengeContext authenticationChallengeContext3 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, actionExecutedContext.Result);
41 this.InvokeActionResultWithFilters(controllerContext, filters.ResultFilters, authenticationChallengeContext3.Result ?? actionExecutedContext.Result); 执行 ActionResult，同时执行方法前后的 IResultFilter
42 }
43 }
44 }
45 catch (ThreadAbortException)
46 {
47 throw;
48 }
49 catch (Exception exception)
50 {
51 ExceptionContext exceptionContext = this.InvokeExceptionFilters(controllerContext, filters.ExceptionFilters, exception);
52 if (!exceptionContext.ExceptionHandled)
53 {
54 throw;
55 }
56 this.InvokeActionResult(controllerContext, exceptionContext.Result);//异常过滤器的执行。
57 }
58 return true;
59 }
60 return false;
61 }
B、当选择完合适的Action后，接着就是 ModelBinder（默认是System.Web.Mvc.DefaultModelBinder），它会从http请求的参数中提取数据并实现类型转换，数据校验（例如是否必填，数据格式等）以及是否自动装配到action方法的参数中System.Web.Mvc.DefaultModelBinder
1 protected virtual IDictionary<string, object> GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
2 {
3 Dictionary<string, object> dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
4 ParameterDescriptor[] parameters = actionDescriptor.GetParameters();
5 for (int i = 0; i < parameters.Length; i++)
6 {
7 ParameterDescriptor parameterDescriptor = parameters[i];
8 dictionary[parameterDescriptor.ParameterName] = this.GetParameterValue(controllerContext, parameterDescriptor);
9 }
10 return dictionary;
11 }
1 protected virtual object GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor)
2 {
3 Type parameterType = parameterDescriptor.ParameterType;
4 IModelBinder arg_92_0 = this.GetModelBinder(parameterDescriptor);
5 IValueProvider valueProvider = controllerContext.Controller.ValueProvider;
6 string modelName = parameterDescriptor.BindingInfo.Prefix ?? parameterDescriptor.ParameterName;
7 Predicate<string> propertyFilter = ControllerActionInvoker.GetPropertyFilter(parameterDescriptor);
8 ModelBindingContext bindingContext = new ModelBindingContext
9 {
10 FallbackToEmptyPrefix = parameterDescriptor.BindingInfo.Prefix == null,
11 ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, parameterType),
12 ModelName = modelName,
13 ModelState = controllerContext.Controller.ViewData.ModelState,
14 PropertyFilter = propertyFilter,
15 ValueProvider = valueProvider
16 };
17 return arg_92_0.BindModel(controllerContext, bindingContext) ?? parameterDescriptor.DefaultValue;
18 }
C、Authentication Filter是mvc5中新增的一个Filter，它会先于authorization filter执行，目的是对访问用户的认证。在MVC5之前，认证和授权都是通过authorization filter来实现的，但现在这2个操作就分开来了，各自管各自喽。
1 AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);
2 if (authenticationContext.Result != null)
3 {
4 AuthenticationChallengeContext authenticationChallengeContext = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, authenticationContext.Result);
5 this.InvokeActionResult(controllerContext, authenticationChallengeContext.Result ?? authenticationContext.Result);
6 }
D、Action filters有2个方法OnActionExecuting和OnActionExecuted分别在action执行前后执行。我们也可以通过实现IActionFilter接口来实现你个性化的过滤机制
1 protected virtual ActionExecutedContext InvokeActionMethodWithFilters(ControllerContext controllerContext, IList<IActionFilter> filters, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters)
2 {
3 ActionExecutingContext preContext = new ActionExecutingContext(controllerContext, actionDescriptor, parameters);
4 Func<ActionExecutedContext> seed = () => new ActionExecutedContext(controllerContext, actionDescriptor, false, null)
5 {
6 Result = this.InvokeActionMethod(controllerContext, actionDescriptor, parameters)
7 };
8 return filters.Reverse<IActionFilter>().Aggregate(seed, (Func<ActionExecutedContext> next, IActionFilter filter) => () => ControllerActionInvoker.InvokeActionMethodFilter(filter, preContext, next))();
9 }
E、接下来就是执行我们平时在Action方法中写的代码了（根据请求相应结果）
1 protected virtual ActionResult InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters)
2 {
3 object actionReturnValue = actionDescriptor.Execute(controllerContext, parameters);
4 return this.CreateActionResult(controllerContext, actionDescriptor, actionReturnValue);
5 }
（4）、ActionResult 执行模块。
A、在 ActionResult 执行前后，仍然会有一个filter（IResultFilter），同样的，通过实现 IResultFilter 接口你可以定制自己的过滤逻辑。
1 namespace System.Web.Mvc
2 {
3 /// <summary>Defines the methods that are required for a result filter.</summary>
4 public interface IResultFilter
5 {
6 /// <summary>Called before an action result executes.</summary>
7 /// <param name="filterContext">The filter context.</param>
8 void OnResultExecuting(ResultExecutingContext filterContext);
9
10 /// <summary>Called after an action result executes.</summary>
11 /// <param name="filterContext">The filter context.</param>
12 void OnResultExecuted(ResultExecutedContext filterContext);
13 }
14 }
B、ActionResult 就是把处理的用户请求结果返回。因此 ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult就是具体的返回类型。
C、上面的返回类型可以大致分为2类：ViewResult 和非ViewResult。对于需要生成html页面给客户端的划到ViewResult，而其他的例如返回文本，json数据等则划分到非ViewResult，对于非ViewResult直接返回就可以了。
View的初始化和渲染呈现
A、对于 ViewResult 最终是由合适的 View Engine 通过调用 IView 的 Render() 方法来渲染的：
1 namespace System.Web.Mvc
2 {
3 /// <summary>Defines the methods that are required for a view engine.</summary>
4 public interface IViewEngine
5 {
6 /// <summary>Finds the specified partial view by using the specified controller context.</summary>
7 /// <returns>The partial view.</returns>
8 /// <param name="controllerContext">The controller context.</param>
9 /// <param name="partialViewName">The name of the partial view.</param>
10 /// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param>
11 ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache);
12
13 /// <summary>Finds the specified view by using the specified controller context.</summary>
14 /// <returns>The page view.</returns>
15 /// <param name="controllerContext">The controller context.</param>
16 /// <param name="viewName">The name of the view.</param>
17 /// <param name="masterName">The name of the master.</param>
18 /// <param name="useCache">true to specify that the view engine returns the cached view, if a cached view exists; otherwise, false.</param>
19 ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache);
20
21 /// <summary>Releases the specified view by using the specified controller context.</summary>
22 /// <param name="controllerContext">The controller context.</param>
23 /// <param name="view">The view.</param>
24 void ReleaseView(ControllerContext controllerContext, IView view);
25 }
26 }
1 namespace System.Web.Mvc
2 {
3 /// <summary>Defines the methods that are required for a view.</summary>
4 public interface IView
5 {
6 /// <summary>Renders the specified view context by using the specified the writer object.</summary>
7 /// <param name="viewContext">The view context.</param>
8 /// <param name="writer">The writer object.</param>
9 void Render(ViewContext viewContext, TextWriter writer);
10 }
11 }
B、整个处理过程是由 IViewEngine 来实现的。ASP.NET MVC 默认提供 WebForm（.aspx）和 Razor(.cshtml) 模板引擎，你可以通过实现 IViewEngine 接口来实现自己的 ViewEngine，然后在Application_Start方法中做如下注册：
protected void Application_Start()
{
//移除所有的View引擎包括Webform和Razor
ViewEngines.Engines.Clear();
//注册你自己的View引擎 ViewEngines.Engines.Add(new CustomViewEngine()); }
C、最后，Html Helpers将帮我们生成 input 标签，基于AJAX的 form 等等。
（5）、作为总结，将每个节点主要的代码类贴出来。
这就是整个流程的代码节点，有些是同步执行，有些是异步执行，把握关键点，我这里只是谢了一个大概。
UrlRoutingModule-----RouteCollection.GetRouteData(context)----->IRouteHandler routeHandler = routeData.RouteHandler------》IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext)-----》context.RemapHandler(httpHandler)------->MvcHandler------->ProcessRequest()------>ProcessRequestInit()--------》IController------>controller.Execute(this.RequestContext)-------->ControllerActionInvoker------->InvoleAction()--------->InvoleActionMethod()------->InvoleActionReslt()
三、结束
今天就到这里了，东西虽然不多，但是也写了2个多小时。今天就算自己有学习了一边，大家一定要好好的把握这个流程，对于解决程序中的问题，扩展框架都有很大的好处。我们作为程序员的，应该要知道其一，也要知道其二。没事，看看源码，我们对框架和我们自己的代码有更深的了解。当然，这样做也是有代价的，需要更多的时间去支持，我相信我们的付出是值得。不忘初心，继续努力。老天不会辜负努力的人。
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