HttpApplication的确切执行顺序是:
BeginRequest ->
AuthenticateRequest ->
AuthorizeRequest ->
ResolveRequestCache ->
构建页面(在这里页面构造函数被调用) ->
AcquireRequestState(这里才初始化当前上下文的Session) ->
PreRequestHandlerExecute ->
进入页面执行生命周期(开始Page_Init) ->
PostRequestHandlerExecute ->
ReleaseRequestState ->
UpdateRequestCache ->
EndRequest
http://blog.joycode.com/kaneboy/archive/2004/09/12/33213.aspx