求解惑 ASP.NET源码 HttpApplication初始化有一些不明白的地方

最近在看生命周期的东西 有一点地方不明白 还请了解的朋友帮忙指导一下 多谢

写的比较乱 不知道我描述的你们看不看的懂 下面标红的字体是我的疑问 

 HttpRuntime请求返回HttpApplication得时候

IHttpHandler app = HttpApplicationFactory.GetApplicationInstance(context);

　　

internal static IHttpHandler GetApplicationInstance(HttpContext context) {
            if (_customApplication != null)
                return _customApplication;

            // Check to see if it's a debug auto-attach request
            if (context.Request.IsDebuggingRequest)
                return new HttpDebugHandler();

            _theApplicationFactory.EnsureInited();

            _theApplicationFactory.EnsureAppStartCalled(context);

            return _theApplicationFactory.GetNormalApplicationInstance(context);
        }

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_theApplicationFactory.EnsureAppStartCalled(context); 在调用FireApplicationOnStart方法里 创建了一个HttpApplication GetSpecialApplicationInstance  

internal void InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) {
            // Remember state
            _state = state;

            try {
                //  Remember the context for the initialization
                if (context != null) {
                    _initContext = context;
                    _initContext.ApplicationInstance = this;
                }

                // if we're doing integrated pipeline wireup, then appContext is non-null and we need to init modules and register event subscriptions with IIS
                if (appContext != IntPtr.Zero) {
                    // 1694356: app_offline.htm and <httpRuntime enabled=/> require that we make this check here for integrated mode
                    using (new ApplicationImpersonationContext()) {
                        HttpRuntime.CheckApplicationEnabled();
                    }

                    // retrieve app level culture
                    InitAppLevelCulture();

                    Debug.Trace("PipelineRuntime", "InitSpecial for " + appContext.ToString() + "\n");
                    RegisterEventSubscriptionsWithIIS(appContext, context, handlers);
                }
                else {
                    // retrieve app level culture
                    InitAppLevelCulture();

                    // Hookup event handlers via reflection
                    if (handlers != null) {
                        HookupEventHandlersForApplicationAndModules(handlers);
                    }
                }

                // if we're doing integrated pipeline wireup, then appContext is non-null and we need to register the application (global.asax) event handlers
                if (appContext != IntPtr.Zero) {
                    if (_appPostNotifications != 0 || _appRequestNotifications != 0) {
                        RegisterIntegratedEvent(appContext,
                                                HttpApplicationFactory.applicationFileName,
                                                _appRequestNotifications,
                                                _appPostNotifications,
                                                this.GetType().FullName,
                                                MANAGED_PRECONDITION,
                                                false);
                    }
                }
            }
            finally  {
                _initSpecialCompleted = true;

                //  Do not hold on to the context
                if (_initContext != null) {
                    _initContext.ApplicationInstance = null;
                    _initContext = null;
                }
            }
        }

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在 app.InitSpecial(_state, _eventHandlerMethods, appContext, context);在这个方法里

集成模式下 RegisterEventSubscriptionsWithIIS 调用了HookupEventHandlersForApplicationAndModules 然后再调用各个httpModule的init方法

HookupEventHandlersForApplicationAndModules代码在下面

 在调用HookupEventHandlersForApplicationAndModules这里 有个疑问 获取完addMethod = reflectionEvent.GetAddMethod();之后  addMethod.Invoke(target, new Object[1]{handlerDelegate});这里是httpmodule里+=的执行吗？ 执行这个addMethod函数是干啥的？

经典模式下 只执行了HookupEventHandlersForApplicationAndModules(handlers);

之后再触发application_start之后HttpApplication被回收 回到 return _theApplicationFactory.GetNormalApplicationInstance(context);

又取了一个新的HttpApplication 再InitInternal方法里 集成经典模式 都调用了InitModulesCommon();调用各个httpModule的init方法

对于集成模式下 httpModule的init方法 调用了两次 创建两次HttpApplication调用两次httpModule的init  这样做为啥

private void HookupEventHandlersForApplicationAndModules(MethodInfo[] handlers) {
            _currentModuleCollectionKey = HttpApplicationFactory.applicationFileName;

            if(null == _pipelineEventMasks) {
                Dictionary<string, RequestNotification> dict = new Dictionary<string, RequestNotification>();
                BuildEventMaskDictionary(dict);
                if(null == _pipelineEventMasks) {
                    _pipelineEventMasks = dict;
                }
            }


            for (int i = 0; i < handlers.Length; i++) {
                MethodInfo appMethod = handlers[i];
                String appMethodName = appMethod.Name;
                int namePosIndex = appMethodName.IndexOf('_');
                String targetName = appMethodName.Substring(0, namePosIndex);

                // Find target for method
                Object target = null;

                if (StringUtil.EqualsIgnoreCase(targetName, "Application"))
                    target = this;
                else if (_moduleCollection != null)
                    target = _moduleCollection[targetName];

                if (target == null)
                    continue;

                // Find event on the module type
                Type targetType = target.GetType();
                EventDescriptorCollection events = TypeDescriptor.GetEvents(targetType);
                string eventName = appMethodName.Substring(namePosIndex+1);

                EventDescriptor foundEvent = events.Find(eventName, true);
                if (foundEvent == null
                    && StringUtil.EqualsIgnoreCase(eventName.Substring(0, 2), "on")) {

                    eventName = eventName.Substring(2);
                    foundEvent = events.Find(eventName, true);
                }

                MethodInfo addMethod = null;
                if (foundEvent != null) {
                    EventInfo reflectionEvent = targetType.GetEvent(foundEvent.Name);
                    Debug.Assert(reflectionEvent != null);
                    if (reflectionEvent != null) {
                        addMethod = reflectionEvent.GetAddMethod();
                    }
                }

                if (addMethod == null)
                    continue;

                ParameterInfo[] addMethodParams = addMethod.GetParameters();

                if (addMethodParams.Length != 1)
                    continue;

                // Create the delegate from app method to pass to AddXXX(handler) method

                Delegate handlerDelegate = null;

                ParameterInfo[] appMethodParams = appMethod.GetParameters();

                if (appMethodParams.Length == 0) {
                    // If the app method doesn't have arguments --
                    // -- hookup via intermidiate handler

                    // only can do it for EventHandler, not strongly typed
                    if (addMethodParams[0].ParameterType != typeof(System.EventHandler))
                        continue;

                    ArglessEventHandlerProxy proxy = new ArglessEventHandlerProxy(this, appMethod);
                    handlerDelegate = proxy.Handler;
                }
                else {
                    // Hookup directly to the app methods hoping all types match

                    try {
                        handlerDelegate = Delegate.CreateDelegate(addMethodParams[0].ParameterType, this, appMethodName);
                    }
                    catch {
                        // some type mismatch
                        continue;
                    }
                }

                // Call the AddXXX() to hook up the delegate

                try {
                    addMethod.Invoke(target, new Object[1]{handlerDelegate});
                }
                catch {
                    if (HttpRuntime.UseIntegratedPipeline) {
                        throw;
                    }
                }

                if (eventName != null) {
                    if (_pipelineEventMasks.ContainsKey(eventName)) {
                        if (!StringUtil.StringStartsWith(eventName, "Post")) {
                            _appRequestNotifications |= _pipelineEventMasks[eventName];
                        }
                        else {
                            _appPostNotifications |= _pipelineEventMasks[eventName];
                        }
                    }
                }
            }
        }

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