Asp.Net 详解IIS内部运行原理

Asp.Net 详解IIS内部运行原理

本章节主要讲IIS和Asp.Net 管道内部如何处理客户端Http请求，会较多的以代码的形式讲述，让大家对HttpApplication、HttpHandler、HttpApplicationFactory、Page这几个在处理请求过程中扮演重要角色的对象有更深入的了解。

我们都知道，当用户在浏览器地址栏中输入网址时，该请求会被IIS服务器捕获，如果是请求的是静态页面则由IIS本身处理并直接返回客户端，如果是动态页（*.aspx），通过一序列的前期(这部分处理过程本文不详细讲解，可以参考其他文章)的处理来到.NET运行时，然后交给Aspnet_ispai.dll处理，处理完成后返回处理结果。请求和处理过程可以分为：HttpRuntime->HttpModule->HtppApplicationFactory->HttpApplication->HttpHandlerFactory->HttpHandler->HttpModule->将请求结果返回到客户端。

下面我们通过单步调式跟踪System.Web.Dll源码来分析各个过程中关键处理函数(关于如何单步调式.Net FrameWork 源码我将在后面的文章中给出)

（说明：部分代码只保留了关键代码）

1、首先进入管道运行时中的托管入口函数

IIS集成模式：

在IPipelineRuntime.cs类中请求通知函数：ProcessRequestNotification，并调用ProcessRequestNotificationHelper函数

1. internal static int ProcessRequestNotification(
2. IntPtr rootedObjectsPointer,
3. IntPtr nativeRequestContext,
4. IntPtr moduleData,
5. int flags)
6. {
7. try {
8. //调用ProcessRequestNotificationHelper
9.   return ProcessRequestNotificationHelper(rootedObjectsPointer, nativeRequestContext, moduleData, flags);
10. }
11. catch(Exception e) {
12. ApplicationManager.RecordFatalException(e);
13. throw;
14. }
15. }

2、在ProcessRequestNotificationHelper函数中调用运行时HttpRuntime中的ProcessRequestNotification函数

1. internal static int ProcessRequestNotificationHelper(
2. IntPtr rootedObjectsPointer,
3. IntPtr nativeRequestContext,
4. IntPtr moduleData,
5. int flags)
6. {
7. IIS7WorkerRequest wr = null;
8. HttpContext context = null;
9. RequestNotificationStatus status = RequestNotificationStatus.Continue;
10. RootedObjects root;
11. bool workerRequestWasJustCreated = false;
13. try {
15. status = HttpRuntime.ProcessRequestNotification(wr, context); //调用ProcessRequestNotification函数
16. }
17. finally {
19. }
20. return ( int)status;
22. }

3、在ProcessRequestNotification中调用ProcessRequestNotificationPrivate

4、处理请求通知ProcessRequestNotificationPrivate函数中调用了HttpApplicatioinFactory的GetApplicationInstance()函数来获取HttpApplication实例对象，并调用BeginProcessRequestNotification处理请求

1. private RequestNotificationStatus ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) {
2. RequestNotificationStatus status = RequestNotificationStatus.Pending;
3. try {
6. IHttpHandler handler = null;
7. if (context.NeedToInitializeApp()) {
9. try {
10. EnsureFirstRequestInit(context);
11. }
12. catch {
14. }
16. context.Response.InitResponseWriter();
17. handler = HttpApplicationFactory.GetApplicationInstance(context); //获取HttpApplication实例
18. if (handler == null)
19. throw new HttpException(SR.GetString(SR.Unable_create_app_object));
21. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, context.WorkerRequest, handler.GetType().FullName, "Start");
23. HttpApplication app = handler as HttpApplication;
24. if (app != null) {
25. // associate the context with an application instance
26. app.AssignContext(context);
27. }
28. }
31. wr.SynchronizeVariables(context);
33. if (context.ApplicationInstance != null) {
34. // 处理请求
35. IAsyncResult ar = context.ApplicationInstance.BeginProcessRequestNotification(context, _requestNotificationCompletionCallback);
37. if (ar.CompletedSynchronously) {
38. status = RequestNotificationStatus.Continue;
39. }
40. }
41. else if (handler != null) {
42. // HttpDebugHandler is processed here
43. handler.ProcessRequest(context);
44. status = RequestNotificationStatus.FinishRequest;
45. }
46. else {
47. status = RequestNotificationStatus.Continue;
48. }
49. }
50. catch (Exception e) {
52. }
53. return status;
54. }

IIS经典模式：

在ISAPIRuntime.cs类中请求 ProcessRequest函数并调用HttpRuntime.ProcessReques方法

1、HttpRuntime处理请求入口函数

1. public static void ProcessRequest(HttpWorkerRequest wr) {
2. if (wr == null)
3. throw new ArgumentNullException( "wr");
5. if (HttpRuntime.UseIntegratedPipeline) {
6. throw new PlatformNotSupportedException(SR.GetString(SR.Method_Not_Supported_By_Iis_Integrated_Mode, "HttpRuntime.ProcessRequest"));
7. }
9. ProcessRequestNoDemand(wr); //调用ProcessRequestNoDemand函数
10. }

2、ProcessRequestNoDemand函数，调用ProcessRequestNow函数

1. internal static void ProcessRequestNoDemand(HttpWorkerRequest wr) {
2. RequestQueue rq = _theRuntime._requestQueue;
4. wr.UpdateInitialCounters();
6. if (rq != null) // could be null before first request
7. wr = rq.GetRequestToExecute(wr);
9. if (wr != null) {
10. CalculateWaitTimeAndUpdatePerfCounter(wr);
11. wr.ResetStartTime();
12. ProcessRequestNow(wr);调用ProcessRequestNow
13. }
14. }

3、ProcessRequestNow函数，调用ProcessRequestInternal

1. internal static void ProcessRequestNow(HttpWorkerRequest wr)
2. {
3. _theRuntime.ProcessRequestInternal(wr); //调用ProcessRequestInternal
4. }

4、ProcessRequestInternal函数，调用HttpApplicatioinFactory的GetApplicationInstance()函数来获取HttpApplication实例对象

1. private void ProcessRequestInternal(HttpWorkerRequest wr) {
2. // Count active requests
3. Interlocked.Increment( ref _activeRequestCount);
6. // Get application instance
7. IHttpHandler app = HttpApplicationFactory.GetApplicationInstance(context); //获取HttpApplication对象
9. if (app == null)
10. throw new HttpException(SR.GetString(SR.Unable_create_app_object));
12. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_START_HANDLER, context.WorkerRequest, app.GetType().FullName, "Start");
14. if (app is IHttpAsyncHandler) {
15. // asynchronous handler
16. IHttpAsyncHandler asyncHandler = (IHttpAsyncHandler)app;
17. context.AsyncAppHandler = asyncHandler;
18. //来到了真正处理请求步骤
19. asyncHandler.BeginProcessRequest(context, _handlerCompletionCallback, context);
20. }
21. else {
22. // synchronous handler
23. app.ProcessRequest(context);
24. FinishRequest(context.WorkerRequest, context, null);
25. }
26. }
27. catch (Exception e) {
28. context.Response.InitResponseWriter();
29. FinishRequest(wr, context, e);
30. }
31. }

说明：以上4个步骤集成模式和经典模式分不同的函数执行，从下面开始两种模式调用相同的函数，只是在函数中针对不同的模式进行不同的处理

5、进入HttpApplicationFactory，调用GetNormalApplicationInstance函数

1. internal static IHttpHandler GetApplicationInstance(HttpContext context) {
2. if (_customApplication != null)
3. return _customApplication;
5.   if (context.Request.IsDebuggingRequest)
6. return new HttpDebugHandler();
8. _theApplicationFactory.EnsureInited();
10. _theApplicationFactory.EnsureAppStartCalled(context);
12. return _theApplicationFactory.GetNormalApplicationInstance(context); //返回HttpApplication实例
13. }

6、进入GetNormalApplicationInstance函数，调用InitInternal初始化HttpApplication内部对象

1. private HttpApplication GetNormalApplicationInstance(HttpContext context) {
2. HttpApplication app = null;
4. lock (_freeList) {
5. if (_numFreeAppInstances > 0) {
6. app = (HttpApplication)_freeList.Pop();
7. _numFreeAppInstances--;
9. if (_numFreeAppInstances < _minFreeAppInstances) {
10. _minFreeAppInstances = _numFreeAppInstances;
11. }
12. }
13. }
15. if (app == null) {
16. // If ran out of instances, create a new one
17. app = (HttpApplication)HttpRuntime.CreateNonPublicInstance(_theApplicationType);
19. using ( new ApplicationImpersonationContext()) {
20. app.InitInternal(context, _state, _eventHandlerMethods); //初始化Application内部对象
21. }
22. }
24. if (AppSettings.UseTaskFriendlySynchronizationContext) {
25. // When this HttpApplication instance is no longer in use, recycle it.
26. app.ApplicationInstanceConsumersCounter = new CountdownTask( 1); // representing required call to HttpApplication.ReleaseAppInstance
27. app.ApplicationInstanceConsumersCounter.Task.ContinueWith((_, o) => RecycleApplicationInstance((HttpApplication)o), app, TaskContinuationOptions.ExecuteSynchronously);
28. }
29. return app;
30. }

7、进入HttpApplication,调用InitInternal函数来初始化Application内部对象。初始化HttpModule和建立处理执行步骤

1. internal void InitInternal(HttpContext context, HttpApplicationState state, MethodInfo[] handlers) {
2. Debug.Assert(context != null, "context != null");
4. // Remember state
5. _state = state;
7. PerfCounters.IncrementCounter(AppPerfCounter.PIPELINES);
9. try {
10. try {
11. // Remember context for config lookups
12. _initContext = context;
13. _initContext.ApplicationInstance = this;
15. // Set config path to be application path for the application initialization
16. context.ConfigurationPath = context.Request.ApplicationPathObject;
18. // keep HttpContext.Current working while running user code
19. using ( new DisposableHttpContextWrapper(context)) {
21. // Build module list from config 根据IIS集成模式和经典模式初始化HttpMudule
22. if (HttpRuntime.UseIntegratedPipeline) { //集成模式
24. Debug.Assert(_moduleConfigInfo != null, "_moduleConfigInfo != null");
25. Debug.Assert(_moduleConfigInfo.Count >= 0, "_moduleConfigInfo.Count >= 0");
27. try {
28. context.HideRequestResponse = true;
29. _hideRequestResponse = true;
30. InitIntegratedModules(); //集成模式初始化HttpModule
31. }
32. finally {
33. context.HideRequestResponse = false;
34. _hideRequestResponse = false;
35. }
36. }
37. else { //经典模式
38. InitModules(); //经典模式初始化HttpModule
40. // this is used exclusively for integrated mode
41. Debug.Assert( null == _moduleContainers, "null == _moduleContainers");
42. }
44. // Hookup event handlers via reflection
45. if (handlers != null)
46. HookupEventHandlersForApplicationAndModules(handlers);
48. // Initialization of the derived class
49. _context = context;
50. if (HttpRuntime.UseIntegratedPipeline && _context != null) {
51. _context.HideRequestResponse = true;
52. }
53. _hideRequestResponse = true;
55. try {
56. Init();
57. }
58. catch (Exception e) {
59. RecordError(e);
60. }
61. }
63. if (HttpRuntime.UseIntegratedPipeline && _context != null) {
64. _context.HideRequestResponse = false;
65. }
66. _hideRequestResponse = false;
67. _context = null;
68. _resumeStepsWaitCallback= new WaitCallback( this.ResumeStepsWaitCallback);
70. // Construct the execution steps array
71. "color:#FF0000;"> if (HttpRuntime.UseIntegratedPipeline) { //集成模式 调用PipelineStepManager
72. "color:#FF0000;">_stepManager = new PipelineStepManager( this);
73. }
74. else {
75. "color:#FF0000;"> _stepManager = new ApplicationStepManager( this); //经典模式 调用 ApplicationStepManager
76. }
78. "color:#FF0000;">_stepManager.BuildSteps(_resumeStepsWaitCallback); //建立执行处理步骤
79. }
80. finally {
81. _initInternalCompleted = true;
83. // Reset config path
84. context.ConfigurationPath = null;
86. // don't hold on to the context
87. _initContext.ApplicationInstance = null;
88. _initContext = null;
89. }
90. }
91. catch { // Protect against exception filters
92. throw;
93. }
94. }

8、初始化HttpModule，包含系统默认的HttpModule和自定义的HttpModule

1）、系统默认的HttpModule：

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\web.config

2）、自定义的HttpModule在网站的Web.config中配置

经典模式：

3. < add name= "mymodule" type= "WebApplication2.myModule"/>

集成模式：

3. < add name= "mymodule" type= "WebApplication2.myModule"/>

3）、经典模式初始化：

1. private void InitModules() {
3. //读取配置文件中HttpModules节点
4.  HttpModulesSection pconfig = RuntimeConfig.GetAppConfig().HttpModules;
6. //获取HttpModule集合
7. HttpModuleCollection moduleCollection = pconfig.CreateModules();
8. HttpModuleCollection dynamicModules = CreateDynamicModules();
10. moduleCollection.AppendCollection(dynamicModules);
11. _moduleCollection = moduleCollection; // don't assign until all ops have succeeded
13. InitModulesCommon(); //调用InitModulesCommon
14. }

4）、初始化各个HttpModule对象.

1. private void InitModulesCommon() {
2. int n = _moduleCollection.Count;
4. for ( int i = 0; i < n; i++) {
5. // remember the module being inited for event subscriptions
6. // we'll later use this for routing
7. _currentModuleCollectionKey = _moduleCollection.GetKey(i);
8. _moduleCollection[i].Init( this); //初始化每个HttpModule
9. }
11. _currentModuleCollectionKey = null;
12. InitAppLevelCulture();
13. }

5）、初始化HttpModule，在Init函数中注册HttpApplication对象的事件，这里举了两个例子

OutputCacheModule.cs  web.config中默认第一个HttpModule

1. void IHttpModule.Init(HttpApplication app) {
2. OutputCacheSection cacheConfig = RuntimeConfig.GetAppConfig().OutputCache;
3. if (cacheConfig.EnableOutputCache) {
4. app.ResolveRequestCache += new EventHandler( this.OnEnter);
5. app.UpdateRequestCache += new EventHandler( this.OnLeave);
6. }
7. }

SessionStateModule.cs web.config中默认第二个HttpModule，实现Session的系统HttpModule

1. public void Init(HttpApplication app) {
2. bool initModuleCalled = false;
3. SessionStateSection config = RuntimeConfig.GetAppConfig().SessionState;
5. if (!s_oneTimeInit) {
6. s_lock.AcquireWriterLock();
7. try {
8. if (!s_oneTimeInit) {
9. InitModuleFromConfig(app, config);
10. initModuleCalled = true;
12. if (!CheckTrustLevel(config))
13. s_trustLevelInsufficient = true;
15. s_timeout = ( int)config.Timeout.TotalMinutes;
17. s_useHostingIdentity = config.UseHostingIdentity;
19. // See if we can try InProc optimization. See inline doc of s_allowInProcOptimization
20. // for details.
21. if (config.Mode == SessionStateMode.InProc &&
22. _usingAspnetSessionIdManager) {
23. s_allowInProcOptimization = true;
24. }
26. if (config.Mode != SessionStateMode.Custom &&
27. config.Mode != SessionStateMode.Off &&
28. !config.RegenerateExpiredSessionId) {
29. s_allowDelayedStateStoreItemCreation = true;
30. }
32. s_configExecutionTimeout = RuntimeConfig.GetConfig().HttpRuntime.ExecutionTimeout;
34. s_configRegenerateExpiredSessionId = config.RegenerateExpiredSessionId;
35. s_configCookieless = config.Cookieless;
36. s_configMode = config.Mode;
38. // The last thing to set in this if-block.
39. s_oneTimeInit = true;
41. Debug.Trace( "SessionStateModuleInit",
42. "Configuration: _mode=" + config.Mode +
43. ";Timeout=" + config.Timeout +
44. ";CookieMode=" + config.Cookieless +
45. ";SqlConnectionString=" + config.SqlConnectionString +
46. ";StateConnectionString=" + config.StateConnectionString +
47. ";s_allowInProcOptimization=" + s_allowInProcOptimization +
48. ";s_allowDelayedStateStoreItemCreation=" + s_allowDelayedStateStoreItemCreation);
50. }
51. }
52. finally {
53. s_lock.ReleaseWriterLock();
54. }
55. }
57. if (!initModuleCalled) {
58. InitModuleFromConfig(app, config);
59. }
61. if (s_trustLevelInsufficient) {
62. throw new HttpException(SR.GetString(SR.Session_state_need_higher_trust));
63. }
64. }

集成模式初始化HttpModule代码我就不贴出来了，大家可以在源码中查看

9、建立处理步骤BuildSteps，将所有要执行的步骤载入到一个IExecutionStep[]集合中，待后面ResumeSteps调用

经典模式：调用ApplicationStepManager类中的BuildSteps函数

1. internal class ApplicationStepManager : StepManager {
2. private IExecutionStep[] _execSteps;
3. private WaitCallback _resumeStepsWaitCallback;
4. private int _currentStepIndex;
5. private int _numStepCalls;
6. private int _numSyncStepCalls;
7. private int _endRequestStepIndex;
9. internal ApplicationStepManager(HttpApplication app): base(app) {
10. }
12. internal override void BuildSteps(WaitCallback stepCallback )
13. {
14. ArrayList steps = new ArrayList();
15. HttpApplication app = _application;
17. bool urlMappingsEnabled = false;
18. UrlMappingsSection urlMappings = RuntimeConfig.GetConfig().UrlMappings;
19. urlMappingsEnabled = urlMappings.IsEnabled && ( urlMappings.UrlMappings.Count > 0 );
21. steps.Add( new ValidateRequestExecutionStep(app));
22. steps.Add( new ValidatePathExecutionStep(app));
24. if (urlMappingsEnabled)
25. steps.Add( new UrlMappingsExecutionStep(app)); // url mappings
27. app.CreateEventExecutionSteps(HttpApplication.EventBeginRequest, steps);
28. app.CreateEventExecutionSteps(HttpApplication.EventAuthenticateRequest, steps);
29. app.CreateEventExecutionSteps(HttpApplication.EventDefaultAuthentication, steps);
30. app.CreateEventExecutionSteps(HttpApplication.EventPostAuthenticateRequest, steps);
31. app.CreateEventExecutionSteps(HttpApplication.EventAuthorizeRequest, steps);
32. app.CreateEventExecutionSteps(HttpApplication.EventPostAuthorizeRequest, steps);
33. app.CreateEventExecutionSteps(HttpApplication.EventResolveRequestCache, steps);
34. app.CreateEventExecutionSteps(HttpApplication.EventPostResolveRequestCache, steps);
35. steps.Add( new MapHandlerExecutionStep(app)); //分配一个Handler
36. app.CreateEventExecutionSteps(HttpApplication.EventPostMapRequestHandler, steps);
37. app.CreateEventExecutionSteps(HttpApplication.EventAcquireRequestState, steps);
38. app.CreateEventExecutionSteps(HttpApplication.EventPostAcquireRequestState, steps);
39. app.CreateEventExecutionSteps(HttpApplication.EventPreRequestHandlerExecute, steps);
40. steps.Add(app.CreateImplicitAsyncPreloadExecutionStep()); // implict async preload step
41. steps.Add( new CallHandlerExecutionStep(app)); // 执行HttpHandler
42. app.CreateEventExecutionSteps(HttpApplication.EventPostRequestHandlerExecute, steps);
43. app.CreateEventExecutionSteps(HttpApplication.EventReleaseRequestState, steps);
44. app.CreateEventExecutionSteps(HttpApplication.EventPostReleaseRequestState, steps);
45. steps.Add( new CallFilterExecutionStep(app)); // filtering
46. app.CreateEventExecutionSteps(HttpApplication.EventUpdateRequestCache, steps);
47. app.CreateEventExecutionSteps(HttpApplication.EventPostUpdateRequestCache, steps);
48. _endRequestStepIndex = steps.Count;
49. app.CreateEventExecutionSteps(HttpApplication.EventEndRequest, steps);
50. steps.Add( new NoopExecutionStep()); // the last is always there
52. _execSteps = new IExecutionStep[steps.Count];
53. steps.CopyTo(_execSteps);
55. // callback for async completion when reposting to threadpool thread
56. _resumeStepsWaitCallback = stepCallback;
57. }

集成模式：调用PipelineStepManager类中的 BuildSteps函数

1. internal override void BuildSteps(WaitCallback stepCallback) {
2. Debug.Trace( "PipelineRuntime", "BuildSteps");
3. //ArrayList steps = new ArrayList();
4. HttpApplication app = _application;
6. // add special steps that don't currently
7. // correspond to a configured handler
9. IExecutionStep materializeStep = new MaterializeHandlerExecutionStep(app);
11. // implicit map step
12. app.AddEventMapping(
13. HttpApplication.IMPLICIT_HANDLER,
14. RequestNotification.MapRequestHandler,
15. false, materializeStep);
17. // implicit async preload step
18. app.AddEventMapping(
19. HttpApplication.IMPLICIT_HANDLER,
20. RequestNotification.ExecuteRequestHandler,
21. false, app.CreateImplicitAsyncPreloadExecutionStep());
23. // implicit handler routing step
24. IExecutionStep handlerStep = new CallHandlerExecutionStep(app);
26. app.AddEventMapping(
27. HttpApplication.IMPLICIT_HANDLER,
28. RequestNotification.ExecuteRequestHandler,
29. false, handlerStep);
31. // implicit handler WebSockets step
32. IExecutionStep webSocketsStep = new TransitionToWebSocketsExecutionStep(app);
34. app.AddEventMapping(
35. HttpApplication.IMPLICIT_HANDLER,
36. RequestNotification.EndRequest,
37. true /* isPostNotification */, webSocketsStep);
39. // add implicit request filtering step
40. IExecutionStep filterStep = new CallFilterExecutionStep(app);
42. // normally, this executes during UpdateRequestCache as a high priority module
43. app.AddEventMapping(
44. HttpApplication.IMPLICIT_FILTER_MODULE,
45. RequestNotification.UpdateRequestCache,
46. false, filterStep);
48. // for error conditions, this executes during LogRequest as a high priority module
49. app.AddEventMapping(
50. HttpApplication.IMPLICIT_FILTER_MODULE,
51. RequestNotification.LogRequest,
52. false, filterStep);
54. _resumeStepsWaitCallback = stepCallback;
55. }

10、真正处理请求阶段， 调用ResumeSteps函数来执行处理步骤

经典模式：

返回到ProcessRequestInternal函数中执行BeginProcessRequest函数

1. IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) {
2. HttpAsyncResult result;
4. // Setup the asynchronous stuff and application variables
5. _context = context;
6. _context.ApplicationInstance = this;
8. _stepManager.InitRequest();
10. // Make sure the context stays rooted (including all async operations)
11. _context.Root();
13. // Create the async result
14. result = new HttpAsyncResult(cb, extraData);
16. // Remember the async result for use in async completions
17. AsyncResult = result;
19. if (_context.TraceIsEnabled)
20. HttpRuntime.Profile.StartRequest(_context);
22. // Start the application
23. ResumeSteps( null); //执行处理步骤
25. // Return the async result
26. return result;
27. }

ResumeSteps函数，调用ExecuteStepl函数来执行处理步骤

1. internal override void ResumeSteps(Exception error) {
2. bool appCompleted = false;
3. bool stepCompletedSynchronously = true;
4. HttpApplication app = _application;
5. CountdownTask appInstanceConsumersCounter = app.ApplicationInstanceConsumersCounter;
6. HttpContext context = app.Context;
7. ThreadContext threadContext = null;
8. AspNetSynchronizationContextBase syncContext = context.SyncContext;
10. Debug.Trace( "Async", "HttpApplication.ResumeSteps");
12. try {
13. if (appInstanceConsumersCounter != null) {
14. appInstanceConsumersCounter.MarkOperationPending(); // ResumeSteps call started
15. }
17. using (syncContext.AcquireThreadLock()) {
19. //执行步骤
20. error = app.ExecuteStep(_execSteps[_currentStepIndex], ref stepCompletedSynchronously);
22. }
23. }

集成模式：

返回到ProcessRequestNotificationPrivate函数，执行BeginProcessRequestNotification

BeginProcessRequestNotification函数，调用ResumeSteps执行处理步骤

1. internal IAsyncResult BeginProcessRequestNotification(HttpContext context, AsyncCallback cb)
2. {
3. if ( this._context == null)
4. {
5. this.AssignContext(context);
6. }
7. context.CurrentModuleEventIndex = -1;
8. HttpAsyncResult result = new HttpAsyncResult(cb, context);
9. context.NotificationContext.AsyncResult = result;
10. this.ResumeSteps( null); //开始执行处理步骤
11. return result;
12. }

 ResumeSteps

1. // PipelineStepManager::ResumeSteps
2. // called from IIS7 (on IIS thread) via BeginProcessRequestNotification
3. // or from an async completion (on CLR thread) via HttpApplication::ResumeStepsFromThreadPoolThread
4. // This attribute prevents undesirable 'just-my-code' debugging behavior (VSWhidbey 404406/VSWhidbey 609188)
5. [ System.Diagnostics.DebuggerStepperBoundaryAttribute]
6. internal override void ResumeSteps(Exception error) {
7. HttpContext context = _application.Context;
8. IIS7WorkerRequest wr = context.WorkerRequest as IIS7WorkerRequest;
9. AspNetSynchronizationContextBase syncContext = context.SyncContext;
11. RequestNotificationStatus status = RequestNotificationStatus.Continue;
12. ThreadContext threadContext = null;
13. bool needToDisassociateThreadContext = false;
14. bool isSynchronousCompletion = false;
15. bool needToComplete = false;
16. bool stepCompletedSynchronously = false;
17. int currentModuleLastEventIndex = _application.CurrentModuleContainer.GetEventCount(context.CurrentNotification, context.IsPostNotification) - 1;
18. CountdownTask appInstanceConsumersCounter = _application.ApplicationInstanceConsumersCounter;
20. using (context.RootedObjects.WithinTraceBlock()) {
22. error = _application.ExecuteStep(step, ref stepCompletedSynchronously); //执行处理步骤
24. }
25. }

11、ExecuteStep执行BuildSteps中的各个步骤

1. internal Exception ExecuteStep(IExecutionStep step, ref bool completedSynchronously) {
2. Exception error = null;
4. try {
5. try {
6. if (step.IsCancellable) {
7. _context.BeginCancellablePeriod(); // request can be cancelled from this point
9. try {
10. step.Execute();
11. }
12. finally {
13. _context.EndCancellablePeriod(); // request can be cancelled until this point
14. }
16. _context.WaitForExceptionIfCancelled(); // wait outside of finally
17. }
18. else {
19. step.Execute();
20. }
22. if (!step.CompletedSynchronously) {
23. completedSynchronously = false;
24. return null;
25. }
26. }
29. }

这里贴出了两个很重要的步骤：获取HttpHandler（MaterializeHandlerExecutionStep）和执行HttpHandler（CallHandlerExecutionStep）

经典模式：

MapHandlerExecutionStep

1. // execution step -- map HTTP handler (used to be a separate module)
2. internal class < span style= "color:#FF0000;">MapHandlerExecutionStep : IExecutionStep {
3. private HttpApplication _application;
5. internal MapHandlerExecutionStep(HttpApplication app) {
6. _application = app;
7. }
9. void IExecutionStep.Execute() {
10. HttpContext context = _application.Context;
11. HttpRequest request = context.Request;
13. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_ENTER, context.WorkerRequest);
14. //获取HttpHandler
15. context.Handler = _application.MapHttpHandler(
16. context,
17. request.RequestType,
18. request.FilePathObject,
19. request.PhysicalPathInternal,
20. false /*useAppConfig*/);
21. Debug.Assert(context.ConfigurationPath == context.Request.FilePathObject, "context.ConfigurationPath (" +
22. context.ConfigurationPath + ") != context.Request.FilePath (" + context.Request.FilePath + ")");
24. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_LEAVE, context.WorkerRequest);
25. }
27. bool IExecutionStep.CompletedSynchronously {
28. get { return true;}
29. }
31. bool IExecutionStep.IsCancellable {
32. get { return false; }
33. }
34. }

MapHttpHandler获取处理请求的HttpHandler

1. internal IHttpHandler MapHttpHandler(HttpContext context, string requestType, VirtualPath path, string pathTranslated, bool useAppConfig)
2. {
3. IHttpHandler handler = (context.ServerExecuteDepth == 0) ? context.RemapHandlerInstance : null;
4. using ( new ApplicationImpersonationContext())
5. {
6. if (handler != null)
7. {
8. return handler;
9. }
10. HttpHandlerAction mapping = this.GetHandlerMapping(context, requestType, path, useAppConfig);
11. if (mapping == null)
12. {
13. PerfCounters.IncrementCounter(AppPerfCounter.REQUESTS_NOT_FOUND);
14. PerfCounters.IncrementCounter(AppPerfCounter.REQUESTS_FAILED);
15. throw new HttpException(SR.GetString( "Http_handler_not_found_for_request_type", new object[] { requestType }));
16. }
17. IHttpHandlerFactory factory = this.GetFactory(mapping); //获取HttpHandlerFactory对象，如果网站Web.config中自定义了HttpHandlerFactory对象，则会覆盖系统默认的
18. try
19. {
20. IHttpHandlerFactory2 factory2 = factory as IHttpHandlerFactory2;
21. if (factory2 != null)
22. {
23. handler = factory2.GetHandler(context, requestType, path, pathTranslated); //获取HttpHandler对象，如果为自定义的HttpHandlerFactory，则返回自定义HttpHandlerFactory中设置的HttpHandler
24. }
25. else
26. {
27. handler = factory.GetHandler(context, requestType, path.VirtualPathString, pathTranslated);
28. }
29. }
30. catch (FileNotFoundException exception)
31. {
32. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
33. {
34. throw new HttpException( 0x194, null, exception);
35. }
36. throw new HttpException( 0x194, null);
37. }
38. catch (DirectoryNotFoundException exception2)
39. {
40. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
41. {
42. throw new HttpException( 0x194, null, exception2);
43. }
44. throw new HttpException( 0x194, null);
45. }
46. catch (PathTooLongException exception3)
47. {
48. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
49. {
50. throw new HttpException( 0x19e, null, exception3);
51. }
52. throw new HttpException( 0x19e, null);
53. }
54. if ( this._handlerRecycleList == null)
55. {
56. this._handlerRecycleList = new ArrayList();
57. }
58. this._handlerRecycleList.Add( new HandlerWithFactory(handler, factory));
59. }
60. return handler;
61. }

集成模式：

MaterializeHandlerExecutionStep步骤

1. internal class MaterializeHandlerExecutionStep: IExecutionStep {
2. private HttpApplication _application;
4. internal MaterializeHandlerExecutionStep(HttpApplication app) {
5. _application = app;
6. }
8. void IExecutionStep.Execute() {
9. HttpContext context = _application.Context;
10. HttpRequest request = context.Request;
11. IHttpHandler handler = null;
12. string configType = null;
14. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_ENTER, context.WorkerRequest);
16. IIS7WorkerRequest wr = context.WorkerRequest as IIS7WorkerRequest;
18. // Get handler
19. if (context.RemapHandlerInstance != null){
20. //RemapHandler overrides all
21. wr.SetScriptMapForRemapHandler();
22. context.Handler = context.RemapHandlerInstance;
23. }
24. else if (request.RewrittenUrl != null) {
25. // RewritePath, we need to re-map the handler
26. bool handlerExists;
27. configType = wr.ReMapHandlerAndGetHandlerTypeString(context, request.Path, out handlerExists);
28. if (!handlerExists) {
29. // WOS 1973590: When RewritePath is used with missing handler in Integrated Mode,an empty response 200 is returned instead of 404
30. throw new HttpException( 404, SR.GetString(SR.Http_handler_not_found_for_request_type, request.RequestType));
31. }
32. }
33. else {
34. configType = wr.GetManagedHandlerType();
35. }
37. if (!String.IsNullOrEmpty(configType)) {
38. IHttpHandlerFactory factory = _application.GetFactory(configType); //获取HttpHandlerFactory对象
39. string pathTranslated = request.PhysicalPathInternal;
41. try {
42. handler = factory.GetHandler(context, request.RequestType, request.FilePath, pathTranslated); //获取HttpHandler对象
43. }
44. catch (FileNotFoundException e) {
45. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
46. throw new HttpException( 404, null, e);
47. else
48. throw new HttpException( 404, null);
49. }
50. catch (DirectoryNotFoundException e) {
51. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
52. throw new HttpException( 404, null, e);
53. else
54. throw new HttpException( 404, null);
55. }
56. catch (PathTooLongException e) {
57. if (HttpRuntime.HasPathDiscoveryPermission(pathTranslated))
58. throw new HttpException( 414, null, e);
59. else
60. throw new HttpException( 414, null);
61. }
63. context.Handler = handler;
65. // Remember for recycling
66. if (_application._handlerRecycleList == null)
67. _application._handlerRecycleList = new ArrayList();
68. _application._handlerRecycleList.Add( new HandlerWithFactory(handler, factory));
69. }
71. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Infrastructure)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_MAPHANDLER_LEAVE, context.WorkerRequest);
72. }
74. bool IExecutionStep.CompletedSynchronously {
75. get { return true;}
76. }
78. bool IExecutionStep.IsCancellable {
79. get { return false; }
80. }
81. }

12、执行callhandlerexecutestep步骤，调用handler.ProcessRequest(context)，如果HttpHandler类型为Page，则开始Page页生命周期

1. internal class CallHandlerExecutionStep: IExecutionStep {
2. private HttpApplication _application;
3. private AsyncCallback _completionCallback;
4. private IHttpAsyncHandler _handler; // per call
5. private AsyncStepCompletionInfo _asyncStepCompletionInfo; // per call
6. private bool _sync; // per call
8. internal CallHandlerExecutionStep(HttpApplication app) {
9. _application = app;
10. _completionCallback = new AsyncCallback( this.OnAsyncHandlerCompletion);
11. }
13. voidIExecutionStep.Execute()
14. {
15. HttpContext context = _application.Context;
16. IHttpHandler handler = context.Handler;
18. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Information, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_ENTER, context.WorkerRequest);
20. if (handler != null && HttpRuntime.UseIntegratedPipeline) {
21. IIS7WorkerRequest wr = context.WorkerRequest as IIS7WorkerRequest;
22. if (wr != null && wr.IsHandlerExecutionDenied()) {
23. _sync = true;
24. HttpException error = new HttpException( 403, SR.GetString(SR.Handler_access_denied));
25. error.SetFormatter( new PageForbiddenErrorFormatter(context.Request.Path, SR.GetString(SR.Handler_access_denied)));
26. throw error;
27. }
28. }
30. if (handler == null) {
31. _sync = true;
32. }
33. else if (handler is IHttpAsyncHandler) {
34. // asynchronous handler
35. IHttpAsyncHandler asyncHandler = (IHttpAsyncHandler)handler;
37. _sync = false;
38. _handler = asyncHandler;
40. var beginProcessRequestDelegate = AppVerifier.WrapBeginMethod(_application, asyncHandler.BeginProcessRequest);
42. _asyncStepCompletionInfo.Reset();
43. context.SyncContext.AllowVoidAsyncOperations();
44. IAsyncResult ar;
45. try {
46. ar = beginProcessRequestDelegate(context, _completionCallback, null);
47. }
48. catch {
49. // The asynchronous step has completed, so we should disallow further
50. // async operations until the next step.
51. context.SyncContext.ProhibitVoidAsyncOperations();
52. throw;
53. }
55. bool operationCompleted;
56. bool mustCallEndHandler;
57. _asyncStepCompletionInfo.RegisterBeginUnwound(ar, out operationCompleted, out mustCallEndHandler);
59. if (operationCompleted) {
60. _sync = true;
61. _handler = null; // not to remember
63. // The asynchronous step has completed, so we should disallow further
64. // async operations until the next step.
65. context.SyncContext.ProhibitVoidAsyncOperations();
67. try {
68. if (mustCallEndHandler) {
69. asyncHandler.EndProcessRequest(ar);
70. }
72. _asyncStepCompletionInfo.ReportError();
73. }
74. finally {
75. SuppressPostEndRequestIfNecessary(context);
77. // In Integrated mode, generate the necessary response headers
78. // after the ASP.NET handler runs
79. context.Response.GenerateResponseHeadersForHandler();
80. }
82. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Information, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_LEAVE, context.WorkerRequest);
83. }
84. }
85. else {
86. //同步 handler
87. _sync = true;
89. context.SyncContext.SetSyncCaller();
91. try {
92. handler.ProcessRequest(context); //开始Page页面生命周期
93. }
94. finally {
95. context.SyncContext.ResetSyncCaller();
96. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Information, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_HTTPHANDLER_LEAVE, context.WorkerRequest);
98. SuppressPostEndRequestIfNecessary(context);
100. context.Response.GenerateResponseHeadersForHandler();
101. }
102. }
103. }
105. bool IExecutionStep.CompletedSynchronously {
106. get { return _sync;}
107. }
109. bool IExecutionStep.IsCancellable {
110. // launching of async handler should not be cancellable
111. get { return (_application.Context.Handler is IHttpAsyncHandler) ? false : true; }
112. }
113. }

13、进入Page类的 ProcessRequest方法开始处理请求

1. private void ProcessRequest() {
2. // culture needs to be saved/restored only on synchronous pages (if at all)
3. // save culture
4. Thread currentThread = Thread.CurrentThread;
5. CultureInfo prevCulture = currentThread.CurrentCulture;
6. CultureInfo prevUICulture = currentThread.CurrentUICulture;
8. try {
9. ProcessRequest( true /*includeStagesBeforeAsyncPoint*/, true /*includeStagesAfterAsyncPoint*/); //调用ProcessRequest函数
10. }
11. finally {
12. // restore culture
13. RestoreCultures(currentThread, prevCulture, prevUICulture);
14. }
15. }

14、进入ProcessRequest,调用ProcessRequestMain函数

1. private void ProcessRequest(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) {
2. // Initialize the object and build the tree of controls.
3. // This must happen *after* the intrinsics have been set.
4. // On async pages only call Initialize once (ProcessRequest is called twice)
5. if (includeStagesBeforeAsyncPoint) {
6. FrameworkInitialize();
8. this.ControlState = ControlState.FrameworkInitialized;
9. }
11. bool needToCallEndTrace = Context.WorkerRequest is IIS7WorkerRequest;
12. try {
13. try {
14. if (IsTransacted) {
15. ProcessRequestTransacted();
16. }
17. else {
18. // No transactions
19. ProcessRequestMain(includeStagesBeforeAsyncPoint, includeStagesAfterAsyncPoint); //调用ProcessRequestMain函数
20. }
22. if (includeStagesAfterAsyncPoint) {
23. needToCallEndTrace = false;
24. ProcessRequestEndTrace();
25. }
26. }
27. catch (ThreadAbortException) {
28. try {
29. if (needToCallEndTrace)
30. ProcessRequestEndTrace();
31. } catch {}
32. }
33. finally {
34. if (includeStagesAfterAsyncPoint) {
35. ProcessRequestCleanup();
36. }
37. }
38. }
39. catch { throw; } // Prevent Exception Filter Security Issue (ASURT 122835)
40. }

15、进入ProcessRequestMain,开始Page页面主体处理过程

1. private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint) {
2. try {
3. HttpContext con = Context;
5. string exportedWebPartID = null;
7. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin PreInit");
8. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_ENTER, _context.WorkerRequest);
9. PerformPreInit(); //Page页面生命周期的OnPerLoad阶段
10. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_LEAVE, _context.WorkerRequest);
11. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End PreInit");
13. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin Init");
14. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_ENTER, _context.WorkerRequest);
15. InitRecursive( null);
16. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_LEAVE, _context.WorkerRequest);
17. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End Init");
19. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin InitComplete");
20. OnInitComplete(EventArgs.Empty); //Page页面生命周期的OnInitComplete阶段
21. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End InitComplete");
23. if (IsPostBack) {
24. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin LoadState");
25. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_ENTER, _context.WorkerRequest);
26. LoadAllState(); //Page页面生命周期的LoadViewState阶段（加载视图状态）
27. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_LEAVE, _context.WorkerRequest);
28. if (con.TraceIsEnabled) {
29. Trace.Write( "aspx.page", "End LoadState");
30. Trace.Write( "aspx.page", "Begin ProcessPostData");
31. }
33. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_ENTER, _context.WorkerRequest);
34. ProcessPostData(_requestValueCollection, true /* fBeforeLoad */); //Page页面生命周期ProcessPostData阶段（处理回发数据）
35. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_LEAVE, _context.WorkerRequest);
36. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End ProcessPostData");
37. }
39. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin PreLoad");
40. OnPreLoad(EventArgs.Empty); //Page页面生命周期OnPreLoad阶段（预加载）
41. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End PreLoad");
43. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin Load");
44. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_ENTER, _context.WorkerRequest);
45. LoadRecursive(); //Page页面生命周期Load阶段（加载）
46. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_LEAVE, _context.WorkerRequest);
47. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End Load");
49. if (IsPostBack) {
50. // Try process the post data again (ASURT 29045)
51. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin ProcessPostData Second Try");
52. "color:#FF0000;"> ProcessPostData(_leftoverPostData, false /* !fBeforeLoad */); //Page页面生命周期 ProcessPostData阶段
53. if (con.TraceIsEnabled) {
54. Trace.Write( "aspx.page", "End ProcessPostData Second Try");
55. Trace.Write( "aspx.page", "Begin Raise ChangedEvents");
56. }
58. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_ENTER, _context.WorkerRequest);
59. RaiseChangedEvents(); //Page页面生命周期 RaiseChangedEvents阶段（处理回发更改事件）
60. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_LEAVE, _context.WorkerRequest);
61. if (con.TraceIsEnabled) {
62. Trace.Write( "aspx.page", "End Raise ChangedEvents");
63. Trace.Write( "aspx.page", "Begin Raise PostBackEvent");
64. }
65. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_ENTER, _context.WorkerRequest);
66. RaisePostBackEvent(_requestValueCollection); //Page页面生命周期 RaisePostBackEvent阶段（处理回发事件）
67. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_LEAVE, _context.WorkerRequest);
68. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End Raise PostBackEvent");
69. }
71. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin LoadComplete");
72. OnLoadComplete(EventArgs.Empty); //Page页面生命周期 加载完成
73. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End LoadComplete");
75. if (IsPostBack && IsCallback) {
76. PrepareCallback(callbackControlId); //Page页面生命周期 PrepareRender(预呈现)
77. }
78. else if (!IsCrossPagePostBack) {
79. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin PreRender");
80. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_ENTER, _context.WorkerRequest);
81. PreRenderRecursiveInternal();
82. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_LEAVE, _context.WorkerRequest);
83. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End PreRender");
84. }
85. }
87. /// Async Point here
89. if (_legacyAsyncInfo == null || _legacyAsyncInfo.CallerIsBlocking) {
90. // for non-async pages with registered async tasks - run the tasks here
91. // also when running async page via server.execute - run the tasks here
92. ExecuteRegisteredAsyncTasks();
93. }
95. // Make sure RawUrl gets validated.
96. ValidateRawUrlIfRequired();
98. if (includeStagesAfterAsyncPoint) {
99. if (IsCallback) {
100. RenderCallback();
101. return;
102. }
104. if (IsCrossPagePostBack) {
105. return;
106. }
108. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "Begin PreRenderComplete");
109. PerformPreRenderComplete();
110. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End PreRenderComplete");
112. if (con.TraceIsEnabled) {
113. BuildPageProfileTree(EnableViewState);
114. Trace.Write( "aspx.page", "Begin SaveState");
115. }
117. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_ENTER, _context.WorkerRequest);
119. SaveAllState(); //Page页面生命周期 SaveAllState阶段（保存视图状态）
121. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_LEAVE, _context.WorkerRequest);
122. if (con.TraceIsEnabled) {
123. Trace.Write( "aspx.page", "End SaveState");
124. Trace.Write( "aspx.page", "Begin SaveStateComplete");
125. }
126. OnSaveStateComplete(EventArgs.Empty);
127. if (con.TraceIsEnabled) {
128. Trace.Write( "aspx.page", "End SaveStateComplete");
129. Trace.Write( "aspx.page", "Begin Render");
130. }
132. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_ENTER, _context.WorkerRequest);
133. // Special-case Web Part Export so it executes in the same security context as the page itself (VSWhidbey 426574)
134. if (exportedWebPartID != null) {
135. ExportWebPart(exportedWebPartID);
136. }
137. else {
138. RenderControl(CreateHtmlTextWriter(Response.Output)); //Page页面生命周期 Render阶段（呈现）
139. }
141. if (EtwTrace.IsTraceEnabled(EtwTraceLevel.Verbose, EtwTraceFlags.Page)) EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_LEAVE, _context.WorkerRequest);
143. if (con.TraceIsEnabled) Trace.Write( "aspx.page", "End Render");
145. CheckRemainingAsyncTasks( false);
146. }
148. }

至此，整个IIS处理Asp.Net完整请求就结束了，列举了各个关键处理阶段的处理函数。当我们了解.net framework内部处理机制后能够使我们理解Asp.Net运行机制和本质，对开发人员来说这很重要，不能只停留在会用会写的阶段，而且要知道其内部原理。这样不仅可以帮助我们编写更高效的代码,同时可以学习并借鉴微软的面向对象的编程思想，受益颇多！