们可以利用它们在页面请求的过程中加入自己的事件处理程序。那么在一个aspx

页面请求时后台到底做了什么？当然asp.net做了很多事情，过程也比较复杂，本

文主要分析一下大体的流程。总体流程如下：
请求一个页面时首先被WWW服务截获(inetinfo.exe进程)，这个进程首先判断页面

的后缀，然后根据IIS中的配置来决定调用哪个扩展程序，比如aspx的页面就会调

用c:\windows\microsoft.net\framework\v2.0.50727\aspnet_isapi.dll，aspne

t_isapi.dll将请求发送给w3wp.exe进程(我们在调试IIS中网站时就是把VS2005附

加到这个进程上的)。
接下来w3wp.exe进程就会调用.net类库进行具体处理：
ISAPIRuntime-->HttpRuntime-->HttpApplicationFactory-->HttpApplication--

>HttpModule--HttpHandlerFactory-->HttpHandler 这也是本文主要分析的地方

。 下面只是列出主要流程，如果喜欢钻研的同学可以用Reflector去查看
一：ISAPIRuntime
       bool useOOP = iWRType == 1;
        wr = ISAPIWorkerRequest.CreateWorkerRequest(ecb, useOOP);
        wr.Initialize();
        string appPathTranslated = wr.GetAppPathTranslated();
        string appDomainAppPathInternal =

HttpRuntime.AppDomainAppPathInternal;
        if ((appDomainAppPathInternal == null) ||

StringUtil.EqualsIgnoreCase(appPathTranslated,

appDomainAppPathInternal))
        {
            HttpRuntime.ProcessRequestNoDemand(wr);
            return 0;
        }
        

HttpRuntime.ShutdownAppDomain(ApplicationShutdownReason.PhysicalApplica

tionPathChanged, SR.GetString("Hosting_Phys_Path_Changed", new object[]

{ appDomainAppPathInternal, appPathTranslated }));
        return 1;
它的主要作用是调用一些非托管代码生成HttpWorkerRequest对象，该对象包含当

前请求的所有信息，然后传递给HttpRuntime，这里生成的HttpWorkerRequest对

象可以直接在我们的页面中调用的，通过它取得原始的请求信息：
            IServiceProvider provider =

(IServiceProvider)HttpContext.Current;
            HttpWorkerRequest wr =

(HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));
二：HttpRuntime
最主要的就是private void ProcessRequestInternal(HttpWorkerRequest wr)方

法：         context = new HttpContext(wr, false);
        IHttpHandler applicationInstance =

HttpApplicationFactory.GetApplicationInstance(context);
  IHttpAsyncHandler handler2 = (IHttpAsyncHandler) applicationInstance;
  context.AsyncAppHandler = handler2;
  handler2.BeginProcessRequest(context,

this._handlerCompletionCallback, context);
        1、根据HttpWorkerRequest对象生成HttpContext，HttpContext应该大

家都很熟悉的，它包含request、response等属性，在页面中经常会用到的；
2、调用HttpApplicationFactory来生成IHttpHandler(这里生成的是一个默认的H

ttpApplication对象，HttpApplication也是IHttpHandler接口的一个实现)
3、调用HttpApplication对象执行请求
三：HttpApplicationFactory
正如2.2中所提到的，这里主要是生成一个HttpApplication对象：

internal static string GetApplicationFile()
{
     return Path.Combine(HttpRuntime.AppDomainAppPathInternal,

"global.asax");
}
首先会查看是否存在global.asax文件，如果有的话就用它来生成HttpApplicatio

n对象，从这里我们可以看到global.asax的文件名是在asp.net的框架中写死的，

不能修改的。如果这个文件不存在就使用默认的对象。
创建好HttpApplication之后对它进行初始化：
    application = (HttpApplication)

HttpRuntime.CreateNonPublicInstance(this._theApplicationType);
using (ApplicationImpersonationContext context2 = new

ApplicationImpersonationContext())
{
     application.InitInternal(context, this._state,

this._eventHandlerMethods);
}
四、HttpApplication
这个是比较复杂也比较重要的一个对象
首先是执行初始化操作，比较重要的一步就是进行HttpModule的初始化：        

private void InitModules()
        {
            this._moduleCollection =

RuntimeConfig.GetAppConfig().HttpModules.CreateModules();
            this.InitModulesCommon();
        }它会读取web.config中所有HttpModule的配置
在HookupEventHandlersForApplicationAndModules方法中绑定Module的事件处理

程序接着进行事件实际绑定：
if (HttpRuntime.UseIntegratedPipeline)
{
     this._stepManager = new PipelineStepManager(this);
}
else
{
     this._stepManager = new ApplicationStepManager(this);
}
this._stepManager.BuildSteps(this._resumeStepsWaitCallback);
在ApplicationStepManager的BuildSteps方法中可以看到事件的绑定执行顺序：

app.CreateEventExecutionSteps(HttpApplication.EventBeginRequest,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventAuthenticateRequest,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventDefaultAuthenticatio

n, steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostAuthenticateRequ

est, steps);
app.CreateEventExecutionSteps(HttpApplication.EventAuthorizeRequest,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostAuthorizeRequest

, steps);

app.CreateEventExecutionSteps(HttpApplication.EventResolveRequestCache,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostResolveRequestCa

che, steps);
steps.Add(new HttpApplication.MapHandlerExecutionStep(app));

app.CreateEventExecutionSteps(HttpApplication.EventPostMapRequestHandle

r, steps);

app.CreateEventExecutionSteps(HttpApplication.EventAcquireRequestState,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostAcquireRequestSt

ate, steps);

app.CreateEventExecutionSteps(HttpApplication.EventPreRequestHandlerExe

cute, steps);
steps.Add(new HttpApplication.CallHandlerExecutionStep(app));

app.CreateEventExecutionSteps(HttpApplication.EventPostRequestHandlerEx

ecute, steps);

app.CreateEventExecutionSteps(HttpApplication.EventReleaseRequestState,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostReleaseRequestSt

ate, steps);
steps.Add(new HttpApplication.CallFilterExecutionStep(app));
app.CreateEventExecutionSteps(HttpApplication.EventUpdateRequestCache,

steps);

app.CreateEventExecutionSteps(HttpApplication.EventPostUpdateRequestCac

he, steps);
this._endRequestStepIndex = steps.Count;
app.CreateEventExecutionSteps(HttpApplication.EventEndRequest, steps);
steps.Add(new HttpApplication.NoopExecutionStep());
注意上面红色标注的MapHandlerExecutionStep(读取所有的HttpHandler配置)、C

allHandlerExecutionStep就是对Handle程序进行处理的，也就是说在web.config

中配置的HttpHandler都是在这里进行处理的，执行顺序如上所示
然后就是调用2.3中的方法执行请求：
Code
        IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext

context, AsyncCallback cb, object extraData)
        {
            this._context = context;
            this._context.ApplicationInstance = this;
            this._stepManager.InitRequest();
            this._context.Root();
            HttpAsyncResult result = new HttpAsyncResult(cb,

extraData);
            this.AsyncResult = result;
            if (this._context.TraceIsEnabled)
            {
                HttpRuntime.Profile.StartRequest(this._context);
            }
            this.ResumeSteps(null);
            return result;
        }
在ResumeSteps中就是执行事件处理程序。

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type="System.Web.Caching.OutputCacheModule"/>
      <add name="Session"

type="System.Web.SessionState.SessionStateModule"/>
      <add name="WindowsAuthentication"

type="System.Web.Security.WindowsAuthenticationModule"/>
      <add name="FormsAuthentication"

type="System.Web.Security.FormsAuthenticationModule"/>
      <add name="PassportAuthentication"

type="System.Web.Security.PassportAuthenticationModule"/>
      <add name="RoleManager"

type="System.Web.Security.RoleManagerModule"/>
      <add name="UrlAuthorization"

type="System.Web.Security.UrlAuthorizationModule"/>
      <add name="FileAuthorization"

type="System.Web.Security.FileAuthorizationModule"/>
      <add name="AnonymousIdentification"

type="System.Web.Security.AnonymousIdentificationModule"/>
      <add name="Profile" type="System.Web.Profile.ProfileModule"/>
      <add name="ErrorHandlerModule"

type="System.Web.Mobile.ErrorHandlerModule, System.Web.Mobile,

Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
      <add name="ServiceModel"

type="System.ServiceModel.Activation.HttpModule, System.ServiceModel,

Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
    </httpModules>
基本使用方法可以参见我的上一篇文章

六、HttpHandlerFactory、HttpHandler
这两个对象在web.config中的配置方法是相同的，默认配置有：
Code
     <add path="*.rules" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.xoml" verb="*"

type="System.ServiceModel.Activation.HttpHandler, System.ServiceModel,

Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"

validate="false"/>
      <add path="trace.axd" verb="*"

type="System.Web.Handlers.TraceHandler" validate="true"/>
      <add path="WebResource.axd" verb="GET"

type="System.Web.Handlers.AssemblyResourceLoader" validate="true"/>
      <add path="*.axd" verb="*" type="System.Web.HttpNotFoundHandler"

validate="true"/>
      <add path="*.aspx" verb="*"

type="System.Web.UI.PageHandlerFactory" validate="true"/>
      <add path="*.ashx" verb="*"

type="System.Web.UI.SimpleHandlerFactory" validate="true"/>
      <add path="*.asmx" verb="*"

type="System.Web.Services.Protocols.WebServiceHandlerFactory,

System.Web.Services, Version=2.0.0.0, Culture=neutral,

PublicKeyToken=b03f5f7f11d50a3a" validate="false"/>
      <add path="*.rem" verb="*"

type="System.Runtime.Remoting.Channels.Http.HttpRemotingHandlerFactory,

System.Runtime.Remoting, Version=2.0.0.0, Culture=neutral,

PublicKeyToken=b77a5c561934e089" validate="false"/>
      <add path="*.soap" verb="*"

type="System.Runtime.Remoting.Channels.Http.HttpRemotingHandlerFactory,

System.Runtime.Remoting, Version=2.0.0.0, Culture=neutral,

PublicKeyToken=b77a5c561934e089" validate="false"/>
      <add path="*.asax" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.ascx" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.master" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.skin" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.browser" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.sitemap" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.dll.config" verb="GET,HEAD"

type="System.Web.StaticFileHandler" validate="true"/>
      <add path="*.exe.config" verb="GET,HEAD"

type="System.Web.StaticFileHandler" validate="true"/>
      <add path="*.config" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.cs" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.csproj" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.vb" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.vbproj" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.webinfo" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.licx" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.resx" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.resources" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.mdb" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.vjsproj" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.java" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.jsl" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.ldb" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.ad" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.dd" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.ldd" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.sd" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.cd" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.adprototype" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.lddprototype" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.sdm" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.sdmDocument" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.mdf" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.ldf" verb="*" type="System.Web.HttpForbiddenHandler"

validate="true"/>
      <add path="*.exclude" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.refresh" verb="*"

type="System.Web.HttpForbiddenHandler" validate="true"/>
      <add path="*.svc" verb="*"

type="System.ServiceModel.Activation.HttpHandler, System.ServiceModel,

Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"

validate="false"/>
      <add path="*" verb="GET,HEAD,POST"

type="System.Web.DefaultHttpHandler" validate="true"/>
      <add path="*" verb="*"

type="System.Web.HttpMethodNotAllowedHandler" validate="true"/>
    </httpHandlers>
要注意的是相同的后缀名配置多次的话，后面的配置会把前面的覆盖。

这里我们重点看一下aspx的配置：System.Web.UI.PageHandlerFactory
这是一个HttpHandlerFactory对象，根据不同的Page生成不同的HttpHandler对象

(我们自己的Page页面都是一个IHttpHandler)：
    Page page = BuildManager.CreateInstanceFromVirtualPath(virtualPath,

typeof(Page), context, true, true) as Page;
    if (page == null)
    {
        return null;
    }
    page.TemplateControlVirtualPath = virtualPath;
    return page;
这里会调用web.config中的buildProviders配置编译页面：
Code
<buildProviders>
        <add extension=".aspx"

type="System.Web.Compilation.PageBuildProvider"/>
        <add extension=".ascx"

type="System.Web.Compilation.UserControlBuildProvider"/>
        <add extension=".master"

type="System.Web.Compilation.MasterPageBuildProvider"/>
        <add extension=".asmx"

type="System.Web.Compilation.WebServiceBuildProvider"/>
        <add extension=".ashx"

type="System.Web.Compilation.WebHandlerBuildProvider"/>
        <add extension=".soap"

type="System.Web.Compilation.WebServiceBuildProvider"/>
        <add extension=".resx"

type="System.Web.Compilation.ResXBuildProvider"/>
        <add extension=".resources"

type="System.Web.Compilation.ResourcesBuildProvider"/>
        <add extension=".wsdl"

type="System.Web.Compilation.WsdlBuildProvider"/>
        <add extension=".xsd"

type="System.Web.Compilation.XsdBuildProvider"/>
        <add extension=".js"

type="System.Web.Compilation.ForceCopyBuildProvider"/>
        <add extension=".lic"

type="System.Web.Compilation.IgnoreFileBuildProvider"/>
        <add extension=".licx"

type="System.Web.Compilation.IgnoreFileBuildProvider"/>
        <add extension=".exclude"

type="System.Web.Compilation.IgnoreFileBuildProvider"/>
        <add extension=".refresh"

type="System.Web.Compilation.IgnoreFileBuildProvider"/>
        <add extension=".xoml"

type="System.ServiceModel.Activation.WorkflowServiceBuildProvider,

System.WorkflowServices, Version=3.5.0.0, Culture=neutral,

PublicKeyToken=31bf3856ad364e35"/>
        <add extension=".svc"

type="System.ServiceModel.Activation.ServiceBuildProvider,

System.ServiceModel, Version=3.0.0.0, Culture=neutral,

PublicKeyToken=b77a5c561934e089"/>
      </buildProviders>

这样就可以进入我们的Page执行了，大的执行顺序可以参见第四部分的描述，它

也就是一个HttpHandler.q

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