一、介紹
我們做開發的，尤其是做微軟技術棧的，有一個方向是跳不過去的，那就是MVC開發。我相信大家，做ASP.NET MVC 開發有的有很長時間，當然，也有剛進入這個行業的。無論如何，如果有人問你，你知道ASP.NET MVC的生命週期嗎？你知道它的來世今生嗎？你知道它和 ASP.NET WEBFORM 有什麼區別嗎?估計，這些問題，有很多人會答不上來，或者說不清楚。今天，我就把我的理解寫出來，也是對我自己學習的一次回顧和總結吧。當然，由於本人能力有限，在寫的過程中也可能會有一些錯誤，希望大家多多包涵，當然，更希望大家能不靈賜教，我們共同進步。
在開始之前，我們先來說說，ASP.NET Web Form 和 Asp.net MVC 有什麼區別，這裡說的區別，當然是本質區別，不是適用語法那個層次的。其實，說起來，ASP.NET WEB FORM 和 ASP.NET MVC 它們兩個沒有本質區別，使用的都是ASP.NET WEB FORM 的管道處理模型，ASP.NET MVC 也是通過擴充套件 IHttpModule 和 IHttpHandler 來實現的，都是基於 ASP.NET 的 HttpApplication 的管道處理模型擴充套件的，在這個層面來說，它們是一樣的。當然，大家不要抬槓，我說的本質區別都是在這個方面，不同意的勿噴。
有人會問，ASP.NET MVC 和 ASP.NET WEBAPI 它們會有什麼不同嗎？好像 WebAPi 能做的，WebMVC都可以完成，第一眼看上去，好像是這樣，但是它們有著本質的不同。WebAPI 的處理管道是重新寫過的，不是基於 HTTPApplication 管道擴充套件的。ASP.NET WEB API 類似專人做專事，它的管道處理模型更高效，並且有了 Restfull 的概念。當然，大家如何向瞭解更細的內容，就需要看原始碼了。或再說回來，到了 NET CORE 時代，二者又融合管道了。
二、MVC生命週期詳述
1、我們既然要說 ASP.NET MVC的生命週期，為了給大家一個整體印象，俗話說，文不如圖，我就貼一張圖，按著箭頭走，相信大家也會不能理解。
2、上圖很簡單，大家按著箭頭走，也能理解的差不多。以下是按著我的理解，劃分了4個模組。
（1）、路由模組
RouteBase 是對路由規則的抽象，也就是說，一個 RouteBase 物件，也就代表了一個條 路由規則。在 ASP.NET MVC 中，有一個唯一的子類實現就是 Route ，它同樣也是路由規則的代表。我們有了路由規則，一定會把這個規則存放在一個地方，這個地方儲存了很多路由規則，這個地方就是 RouteCollection，中文叫“路由集合”，因為這個集合裡面包含的就是 RouteBase 物件。
RouteCollection 就是路由集合，用於儲存路由規則物件，它的定義形式：
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，其實它和 RouteCollection 是一樣的。
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處理管線中的第一站就是路由模組。當請求到達路由模組後，ASP.NET MVC 框架就會根據 RouteTable 中配置的路由模板來匹配當前請求以獲得對應的 Controller 和 Action 資訊。具體的匹配過程就是有UrlRoutingModule(System.Web.Routing.UrlRoutingModule)來實現的。如果遇到一個匹配的規則，就會立刻跳出下面的配置。也就是說，配置過程是有順序的，如果有一個匹配，後面就算有匹配的也不會執行的。
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); 第一步匹配路由規則
57 if (routeData == null)
58 {
59 return;
60 }
61 IRouteHandler routeHandler = routeData.RouteHandler; 第二步：如有匹配，就找到RouteHandler物件，該型別的例項是：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，根據 RouteHandler 物件，找到最終處理請求的 IHttpHandler 的物件，該型別是 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 處理請求。
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 建立模組
經過了路由模組，生成了 RouteData 路由資料，它包含了根據路由規則匹配的 Controller 和 Action。有了路由資料，需要有處理器來處理請求，這個任務就交給了 RouteData 的 RouteHandler 屬性，它的型別是 IRouteHandler，它的值就是MvcRouteHandler，MvcRouteHandler 呼叫 GetHttpHandler 獲取處理請求的 IHttpHandler 物件，在 MVC 框架中就是 MvcHandler，詳細程式碼如下：
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 呼叫 IHttpHandler 型別的呼叫 ProcessRequest() 方法，用於處理請求。
1 protected internal virtual void ProcessRequest(HttpContextBase httpContext)
2 {
3 IController controller;
4 IControllerFactory controllerFactory;
5 this.ProcessRequestInit(httpContext, out controller, out controllerFactory);建立 IControllerFactory，並建立 IController 物件。
6 try
7 {
8 controller.Execute(this.RequestContext);執行Controller，背後就是呼叫相應的 Action 方法。
9 }
10 finally
11 {
12 controllerFactory.ReleaseController(controller);
13 }
14 }
核心處理請求的方法是ProcessRequestInit()，用於建立 IController 和 IControllerFactory 例項。IControllerFactory 的實際型別是：DefaultControllerFactory，該型別用於建立 IController 型別的例項。
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 }
以上加紅的程式碼就是建立 IController 的例項的邏輯。IController 例項建立完成後，判斷是否實現了 IAsyncController 介面，如果是，就非同步執行 Controller 方法的呼叫，否則就同步執行。
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; 判讀是否是需要非同步執行
7 if (asyncController != null)非同步執行
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//同步執行。
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 執行模組，通過 ControllerActionInvoker 呼叫 InvokeAction() 執行其方法。Action 方法的執行也有2個版本，一個是非同步版本，一個是同步版本。由於 ActionInvoker 實現了 IAsyncActionInvoker 介面，所以也是以已方式執行。該型別是 AsyncControllerActionInvoker。
A、當Controller物件被建立之後，緊接著就會執行Controler 物件的 Execute()，其實背後就是呼叫 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); 獲取所有過濾器，全域性的、控制器的和方法的
16 try
17 {
18 AuthenticationContext authenticationContext = this.InvokeAuthenticationFilters(controllerContext, filters.AuthenticationFilters, actionDescriptor);認證過濾器的執行。
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);授權過濾器的執行。
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); 獲取方法執行引數。
39 ActionExecutedContext actionExecutedContext = this.InvokeActionMethodWithFilters(controllerContext, filters.ActionFilters, actionDescriptor, parameterValues); 執行action，同時執行執行方法前後的 IAcctionFilter
40 AuthenticationChallengeContext authenticationChallengeContext3 = this.InvokeAuthenticationFiltersChallenge(controllerContext, filters.AuthenticationFilters, actionDescriptor, actionExecutedContext.Result);
41 this.InvokeActionResultWithFilters(controllerContext, filters.ResultFilters, authenticationChallengeContext3.Result ?? actionExecutedContext.Result); 執行 ActionResult，同時執行方法前後的 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);//異常過濾器的執行。
57 }
58 return true;
59 }
60 return false;
61 }
B、當選擇完合適的Action後，接著就是 ModelBinder（預設是System.Web.Mvc.DefaultModelBinder），它會從http請求的引數中提取資料並實現型別轉換，資料校驗（例如是否必填，資料格式等）以及是否自動裝配到action方法的引數中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中新增的一個Filter，它會先於authorization filter執行，目的是對訪問使用者的認證。在MVC5之前，認證和授權都是通過authorization filter來實現的，但現在這2個操作就分開來了，各自管各自嘍。
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個方法OnActionExecuting和OnActionExecuted分別在action執行前後執行。我們也可以通過實現IActionFilter介面來實現你個性化的過濾機制
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、接下來就是執行我們平時在Action方法中寫的程式碼了（根據請求相應結果）
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 執行模組。
A、在 ActionResult 執行前後，仍然會有一個filter（IResultFilter），同樣的，通過實現 IResultFilter 介面你可以定製自己的過濾邏輯。
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 就是把處理的使用者請求結果返回。因此 ViewResult, PartialViewResult, RedirectToRouteResult, RedirectResult, ContentResult, JsonResult, FileResult and EmptyResult就是具體的返回型別。
C、上面的返回型別可以大致分為2類：ViewResult 和非ViewResult。對於需要生成html頁面給客戶端的劃到ViewResult，而其他的例如返回文字，json資料等則劃分到非ViewResult，對於非ViewResult直接返回就可以了。
View的初始化和渲染呈現
A、對於 ViewResult 最終是由合適的 View Engine 通過呼叫 IView 的 Render() 方法來渲染的：
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、整個處理過程是由 IViewEngine 來實現的。ASP.NET MVC 預設提供 WebForm（.aspx）和 Razor(.cshtml) 模板引擎，你可以通過實現 IViewEngine 介面來實現自己的 ViewEngine，然後在Application_Start方法中做如下注冊：
protected void Application_Start()
{
//移除所有的View引擎包括Webform和Razor
ViewEngines.Engines.Clear();
//註冊你自己的View引擎 ViewEngines.Engines.Add(new CustomViewEngine()); }
C、最後，Html Helpers將幫我們生成 input 標籤，基於AJAX的 form 等等。
（5）、作為總結，將每個節點主要的程式碼類貼出來。
這就是整個流程的程式碼節點，有些是同步執行，有些是非同步執行，把握關鍵點，我這裡只是謝了一個大概。
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、結束
今天就到這裡了，東西雖然不多，但是也寫了2個多小時。今天就算自己有學習了一邊，大家一定要好好的把握這個流程，對於解決程式中的問題，擴充套件框架都有很大的好處。我們作為程式設計師的，應該要知道其一，也要知道其二。沒事，看看原始碼，我們對框架和我們自己的程式碼有更深的瞭解。當然，這樣做也是有代價的，需要更多的時間去支援，我相信我們的付出是值得。不忘初心，繼續努力。老天不會辜負努力的人。