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詳解ASP.NET頁面生命周期

ASP.NET頁面運(yùn)行時(shí)候，頁面將經(jīng)歷一個(gè)生命周期，在生命周期中將執(zhí)行一系列的處理步驟。包括初始化、實(shí)例化控件、還原和維護(hù)狀態(tài)、運(yùn)行時(shí)間處理程序代碼以及進(jìn)行呈現(xiàn)。熟悉頁面生命周期非常重要，這樣我們才能在生命周期的合適階段編寫代碼。如果我們能在寫代碼的時(shí)候想著我們現(xiàn)在是在做生命周期的哪一步那將是非常好的。

幾個(gè)代表性的問題

在開始的時(shí)候我們先思考幾個(gè)問題，看看我們?cè)诿枋鐾觏撁嫔芷诘臅r(shí)候，能不能回答上這幾個(gè)問題

1.為什么在服務(wù)器端能通過this.textbox1.Text獲取到用戶提交過來的數(shù)據(jù)？
2.在Page_Load中Response.Write("hello")查看生成的html代碼原文件，hello在哪里？為什么？
3.有一個(gè)服務(wù)器端的按鈕，設(shè)置了點(diǎn)擊事件，該點(diǎn)擊事件什么時(shí)候執(zhí)行？是先執(zhí)行Page_Load事件還是先執(zhí)行點(diǎn)擊事件？
4.為什么在服務(wù)器端通過this.textbox1.Text設(shè)置值后，客戶端就能顯示出來？

了解ASP.NET請(qǐng)求管道、應(yīng)用程序生命周期、整體運(yùn)行機(jī)制童鞋可能知道，ASP.NET應(yīng)用程序周期中PreRequestHandlerExecute事件與PostRequestHandlerExecute事件之間就是我們的頁面生命周期了，對(duì)于aspx頁面就是一系列的打造頁面控件樹，觸發(fā)各種頁面時(shí)間，對(duì)于一般處理程序ashx就是直接執(zhí)行咱們開發(fā)者寫的ProcessRequest方法了，對(duì)于MVC應(yīng)用程序就是創(chuàng)建控制器工廠，創(chuàng)建控制器對(duì)象，調(diào)用Action那一套了。

下面主要講述的就是ASP.NET WebForm中的頁面的生命周期了。

我們用反編譯工具查看Page類的ProcessRequest方法可以看見先調(diào)用了FrameworkInitialize; FrameworkInitialize里面就是打造了頁面控件樹，然后調(diào)用了ProcessRequestMain，就開始了執(zhí)行整個(gè)頁面生命周期了（其實(shí)就是調(diào)用了一系列的事件方法）（可能部分圖看不見右邊，可在新標(biāo)簽頁中打開圖片）

1.打造頁面控件樹

FrameworkInitialize內(nèi)部調(diào)用了_buildControlTree（）方法

上圖中左邊是前臺(tái)頁面的代碼，右邊是對(duì)應(yīng) 生成的打造控件樹的代碼。中間截取的是生成表單那一部分的代碼。

下面看一張?jiān)韴D

　　瀏覽器的DOM樹是根據(jù)Html標(biāo)簽生成一個(gè)C語言的DOM樹，而ASP.NET服務(wù)器端是用C#打造的一個(gè)控件樹，也是按照DOM結(jié)構(gòu)打造的。本質(zhì)是一樣。服務(wù)器端所有東西都加到頁面對(duì)象的控件集合中去了。標(biāo)簽在服務(wù)器端有對(duì)應(yīng)的控件對(duì)象的時(shí)候就用控件對(duì)象，沒有的時(shí)候就使用LiteralControl進(jìn)行封裝。不管是服務(wù)器控件還是字符串標(biāo)簽（沒有runat="server"的標(biāo)簽）都以控件對(duì)象的方式存在前臺(tái)頁面類的控件集合里面。好處就是生成前臺(tái)頁面的html代碼的時(shí)候，只需要遍歷控件集合里面的每一個(gè)控件對(duì)象的RenderControl方法，每一個(gè)控件都會(huì)調(diào)用自己的Render方法生成對(duì)應(yīng)的Html字符串。那么所有控件的生成的html字符串就還原成一個(gè)頁面的html代碼了?！　?/p>

2.觸發(fā)PerformPreInit事件　

在所有初始化之前初始化了這個(gè)事件，這個(gè)事件主要是初始化了主題，初始化了母版頁

private void PerformPreInit()

{

 this.OnPreInit(EventArgs.Empty);

 this.InitializeThemes();

 this.ApplyMasterPage();

 this._preInitWorkComplete = true;

}

3.觸發(fā)InitRecursive事件

4.觸發(fā)LoadAllState()事件

加載頁面狀態(tài)解析ViewState，將頁面表單中的ViewState進(jìn)行反Base64編碼，反序列化，存在頁面的ViewState屬性中

5.觸發(fā)ProcessPostData(this._requestValueCollection, true)事件

private void ProcessPostData(NameValueCollection postData, bool fBeforeLoad)
{
 if (this._changedPostDataConsumers == null)
 {
 this._changedPostDataConsumers = new ArrayList();
 }
 if (postData != null)
 {
 foreach (string str in postData)
 {
  if ((str != null)  !IsSystemPostField(str))
  {
  Control control = this.FindControl(str);
  if (control == null)
  {
   if (fBeforeLoad)
   {
   if (this._leftoverPostData == null)
   {
    this._leftoverPostData = new NameValueCollection();
   }
   this._leftoverPostData.Add(str, null);
   }
  }
  else
  {
   IPostBackDataHandler postBackDataHandler = control.PostBackDataHandler;
   if (postBackDataHandler == null)
   {
   if (control.PostBackEventHandler != null)
   {
    this.RegisterRequiresRaiseEvent(control.PostBackEventHandler);
   }
   }
   else
   {
   if (postBackDataHandler != null)
   {
    NameValueCollection postCollection = control.CalculateEffectiveValidateRequest() ? this._requestValueCollection : this._unvalidatedRequestValueCollection;
    if (postBackDataHandler.LoadPostData(str, postCollection))
    {
    this._changedPostDataConsumers.Add(control);
    }
   }
   if (this._controlsRequiringPostBack != null)
   {
    this._controlsRequiringPostBack.Remove(str);
   }
   }
  }
  }
 }
 }
 ArrayList list = null;
 if (this._controlsRequiringPostBack != null)
 {
 foreach (string str2 in this._controlsRequiringPostBack)
 {
  Control control2 = this.FindControl(str2);
  if (control2 != null)
  {
  IPostBackDataHandler adapterInternal = control2.AdapterInternal as IPostBackDataHandler;
  if (adapterInternal == null)
  {
   adapterInternal = control2 as IPostBackDataHandler;
  }
  if (adapterInternal == null)
  {
   object[] args = new object[] { str2 };
   throw new HttpException(SR.GetString("Postback_ctrl_not_found", args));
  }
  NameValueCollection values2 = control2.CalculateEffectiveValidateRequest() ? this._requestValueCollection : this._unvalidatedRequestValueCollection;
  if (adapterInternal.LoadPostData(str2, values2))
  {
   this._changedPostDataConsumers.Add(control2);
  }
  }
  else if (fBeforeLoad)
  {
  if (list == null)
  {
   list = new ArrayList();
  }
  list.Add(str2);
  }
 }
 this._controlsRequiringPostBack = list;
 }
}

主要做了兩件事

1）將表單里提交過來的控件數(shù)據(jù)設(shè)置給頁面對(duì)象的控件樹中對(duì)應(yīng)控件的屬性（給前面打造的控件樹里面控件給值），這樣在服務(wù)器端就可以拿到客戶端輸入的值了。

2）將表單里面提交過來的值與ViewState中控件原來的值進(jìn)行比對(duì)，不同則表示要觸發(fā)該控件的Change 事件，則同時(shí)將該控件放到一個(gè)集合（看源碼其實(shí)就是changedPostDataConsumers）中。在后續(xù)執(zhí)行過程中遍歷改集合依次觸發(fā)對(duì)應(yīng)控件的Change事件。

6.觸發(fā)LoadRecursive()事件

大名鼎鼎的Page_Load就是在這里執(zhí)行的。不過是先執(zhí)行頁面本身的Load事件再執(zhí)行頁面控件的Load事件哦,這時(shí)候前面給控件賦的值,表單提交過來的數(shù)據(jù),ViewState等等都可以使用了，IsPostBack的原理就是判斷是否有name為__VIEWSTATE的數(shù)據(jù)提交過來
7.再次觸發(fā)ProcessPostData(this._leftoverPostData, false)事件

這個(gè)事件我在網(wǎng)上看了很多人說是將第一次遺漏下來的，第一次執(zhí)行ProcessPostData沒有涉及到的控件進(jìn)行處理，但是并沒有說明哪些遺漏下來了。為什么第一次沒處理了？最后Google查到是處理我們開發(fā)者在頁面的Page_Load方法中添加的控件。在Page_Load中我們可以自己創(chuàng)建控件對(duì)象加到頁面對(duì)應(yīng)的“C#DOM樹中“，如：在Page_Load中寫
TextBox txt = new TextBox();txt.ID ="myTxtBox";this.form1.Controls.Add(txt);
這就是把開發(fā)者自己創(chuàng)建的控件加在頁面的form1的表單中。當(dāng)然你也可以加上Change事件了創(chuàng)建控件的時(shí)候。執(zhí)行的還是上面那兩件事了。則回發(fā)的時(shí)候可以給開發(fā)者在Page_Lod中手動(dòng)創(chuàng)建的控件還原值。

8.觸發(fā)RaiseChangedEvents事件

循環(huán)遍歷changedPostDataConsumers集合中的所有控件，依次執(zhí)行控件的非點(diǎn)擊回傳事件，比如文本框的改變事件等　　　　　　

9.觸發(fā)RaisePostBackEvent(this._requestValueCollection)事件

執(zhí)行按鈕點(diǎn)擊回傳事件或者驗(yàn)證事件，如果有多個(gè)按鈕，根據(jù)回發(fā)過來的按鈕的 name來判斷觸發(fā)哪個(gè)按鈕的事件，或者觸發(fā)該控件的驗(yàn)證事件
10.觸發(fā)PerformPreRenderComplete事件

循環(huán)遍歷控件樹中所有的控件，根據(jù)每個(gè)控件生成對(duì)應(yīng)的Html代碼，把服務(wù)器控件渲染成普通的html控件。

11.觸發(fā)事件SaveAllState事件

將服務(wù)器端ViewState集合中的內(nèi)容（開發(fā)者自己加的數(shù)據(jù)或控件狀態(tài)信息等）序列化然后Base64編碼然后設(shè)置到客戶端隱藏域__ViewState中

12.RenderControl(this.CreateHtmlTextWriter(this.Response.Output))

把要發(fā)送到客戶端瀏覽器的內(nèi)容設(shè)置到Response.Output，應(yīng)用程序?qū)⑺l(fā)送到客戶端瀏覽器。[/code]

看到這里不知道大家是否已經(jīng)可以清晰地回答開篇提到的幾個(gè)問題了，其實(shí)就是這些事件執(zhí)行的先后順序，頁面生命周期了。”前人植樹，后人乘涼了"

最后附上生命周期ProcessRequest源碼　　

private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint)
{
 try
 {
 HttpContext context = this.Context;
 string str = null;
 if (includeStagesBeforeAsyncPoint)
 {
  if (this.IsInAspCompatMode)
  {
  AspCompatApplicationStep.OnPageStartSessionObjects();
  }
  if (this.PageAdapter != null)
  {
  this._requestValueCollection = this.PageAdapter.DeterminePostBackMode();
  if (this._requestValueCollection != null)
  {
   this._unvalidatedRequestValueCollection = this.PageAdapter.DeterminePostBackModeUnvalidated();
  }
  }
  else
  {
  this._requestValueCollection = this.DeterminePostBackMode();
  if (this._requestValueCollection != null)
  {
   this._unvalidatedRequestValueCollection = this.DeterminePostBackModeUnvalidated();
  }
  }
  string callbackControlID = string.Empty;
  if (this.DetermineIsExportingWebPart())
  {
  if (!RuntimeConfig.GetAppConfig().WebParts.EnableExport)
  {
   throw new InvalidOperationException(SR.GetString("WebPartExportHandler_DisabledExportHandler"));
  }
  str = this.Request.QueryString["webPart"];
  if (string.IsNullOrEmpty(str))
  {
   throw new InvalidOperationException(SR.GetString("WebPartExportHandler_InvalidArgument"));
  }
  if (string.Equals(this.Request.QueryString["scope"], "shared", StringComparison.OrdinalIgnoreCase))
  {
   this._pageFlags.Set(4);
  }
  string str3 = this.Request.QueryString["query"];
  if (str3 == null)
  {
   str3 = string.Empty;
  }
  this.Request.QueryStringText = str3;
  context.Trace.IsEnabled = false;
  }
  if (this._requestValueCollection != null)
  {
  if (this._requestValueCollection["__VIEWSTATEENCRYPTED"] != null)
  {
   this.ContainsEncryptedViewState = true;
  }
  callbackControlID = this._requestValueCollection["__CALLBACKID"];
  if ((callbackControlID != null)  (this._request.HttpVerb == HttpVerb.POST))
  {
   this._isCallback = true;
  }
  else if (!this.IsCrossPagePostBack)
  {
   VirtualPath path = null;
   if (this._requestValueCollection["__PREVIOUSPAGE"] != null)
   {
   try
   {
    path = VirtualPath.CreateNonRelativeAllowNull(DecryptString(this._requestValueCollection["__PREVIOUSPAGE"], Purpose.WebForms_Page_PreviousPageID));
   }
   catch
   {
    this._pageFlags[8] = true;
   }
   if ((path != null)  (path != this.Request.CurrentExecutionFilePathObject))
   {
    this._pageFlags[8] = true;
    this._previousPagePath = path;
   }
   }
  }
  }
  if (this.MaintainScrollPositionOnPostBack)
  {
  this.LoadScrollPosition();
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin PreInit");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_ENTER, this._context.WorkerRequest);
  }
  this.PerformPreInit();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End PreInit");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin Init");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_ENTER, this._context.WorkerRequest);
  }
  this.InitRecursive(null);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End Init");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin InitComplete");
  }
  this.OnInitComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End InitComplete");
  }
  if (this.IsPostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin LoadState");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_ENTER, this._context.WorkerRequest);
  }
  this.LoadAllState();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End LoadState");
   this.Trace.Write("aspx.page", "Begin ProcessPostData");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_ENTER, this._context.WorkerRequest);
  }
  this.ProcessPostData(this._requestValueCollection, true);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End ProcessPostData");
  }
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin PreLoad");
  }
  this.OnPreLoad(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End PreLoad");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin Load");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_ENTER, this._context.WorkerRequest);
  }
  this.LoadRecursive();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End Load");
  }
  if (this.IsPostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin ProcessPostData Second Try");
  }
  this.ProcessPostData(this._leftoverPostData, false);
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End ProcessPostData Second Try");
   this.Trace.Write("aspx.page", "Begin Raise ChangedEvents");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_ENTER, this._context.WorkerRequest);
  }
  this.RaiseChangedEvents();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Raise ChangedEvents");
   this.Trace.Write("aspx.page", "Begin Raise PostBackEvent");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_ENTER, this._context.WorkerRequest);
  }
  this.RaisePostBackEvent(this._requestValueCollection);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Raise PostBackEvent");
  }
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin LoadComplete");
  }
  this.OnLoadComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End LoadComplete");
  }
  if (this.IsPostBack  this.IsCallback)
  {
  this.PrepareCallback(callbackControlID);
  }
  else if (!this.IsCrossPagePostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin PreRender");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_ENTER, this._context.WorkerRequest);
  }
  this.PreRenderRecursiveInternal();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End PreRender");
  }
  }
 }
 if ((this._legacyAsyncInfo == null) || this._legacyAsyncInfo.CallerIsBlocking)
 {
  this.ExecuteRegisteredAsyncTasks();
 }
 this.ValidateRawUrlIfRequired();
 if (includeStagesAfterAsyncPoint)
 {
  if (this.IsCallback)
  {
  this.RenderCallback();
  }
  else if (!this.IsCrossPagePostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin PreRenderComplete");
  }
  this.PerformPreRenderComplete();
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End PreRenderComplete");
  }
  if (context.TraceIsEnabled)
  {
   this.BuildPageProfileTree(this.EnableViewState);
   this.Trace.Write("aspx.page", "Begin SaveState");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_ENTER, this._context.WorkerRequest);
  }
  this.SaveAllState();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End SaveState");
   this.Trace.Write("aspx.page", "Begin SaveStateComplete");
  }
  this.OnSaveStateComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End SaveStateComplete");
   this.Trace.Write("aspx.page", "Begin Render");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_ENTER, this._context.WorkerRequest);
  }
  if (str != null)
  {
   this.ExportWebPart(str);
  }
  else
  {
   this.RenderControl(this.CreateHtmlTextWriter(this.Response.Output));
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Render");
  }
  this.CheckRemainingAsyncTasks(false);
  }
 }
 }
 catch (ThreadAbortException exception1)
 {
 HttpApplication.CancelModuleException exceptionState = exception1.ExceptionState as HttpApplication.CancelModuleException;
 if ((((includeStagesBeforeAsyncPoint  includeStagesAfterAsyncPoint)  (this._context.Handler == this))  ((this._context.ApplicationInstance != null)  (exceptionState != null)))  !exceptionState.Timeout)
 {
  this._context.ApplicationInstance.CompleteRequest();
  ThreadResetAbortWithAssert();
 }
 else
 {
  this.CheckRemainingAsyncTasks(true);
  throw;
 }
 }
 catch (ConfigurationException)
 {
 throw;
 }
 catch (Exception exception2)
 {
 PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_DURING_REQUEST);
 PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_TOTAL);
 if (!this.HandleError(exception2))
 {
  throw;
 }
 }
}

 

 
 private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint)
{
 try
 {
 HttpContext context = this.Context;
 string str = null;
 if (includeStagesBeforeAsyncPoint)
 {
  if (this.IsInAspCompatMode)
  {
  AspCompatApplicationStep.OnPageStartSessionObjects();
  }
  if (this.PageAdapter != null)
  {
  this._requestValueCollection = this.PageAdapter.DeterminePostBackMode();
  if (this._requestValueCollection != null)
  {
   this._unvalidatedRequestValueCollection = this.PageAdapter.DeterminePostBackModeUnvalidated();
  }
  }
  else
  {
  this._requestValueCollection = this.DeterminePostBackMode();
  if (this._requestValueCollection != null)
  {
   this._unvalidatedRequestValueCollection = this.DeterminePostBackModeUnvalidated();
  }
  }
  string callbackControlID = string.Empty;
  if (this.DetermineIsExportingWebPart())
  {
  if (!RuntimeConfig.GetAppConfig().WebParts.EnableExport)
  {
   throw new InvalidOperationException(SR.GetString("WebPartExportHandler_DisabledExportHandler"));
  }
  str = this.Request.QueryString["webPart"];
  if (string.IsNullOrEmpty(str))
  {
   throw new InvalidOperationException(SR.GetString("WebPartExportHandler_InvalidArgument"));
  }
  if (string.Equals(this.Request.QueryString["scope"], "shared", StringComparison.OrdinalIgnoreCase))
  {
   this._pageFlags.Set(4);
  }
  string str3 = this.Request.QueryString["query"];
  if (str3 == null)
  {
   str3 = string.Empty;
  }
  this.Request.QueryStringText = str3;
  context.Trace.IsEnabled = false;
  }
  if (this._requestValueCollection != null)
  {
  if (this._requestValueCollection["__VIEWSTATEENCRYPTED"] != null)
  {
   this.ContainsEncryptedViewState = true;
  }
  callbackControlID = this._requestValueCollection["__CALLBACKID"];
  if ((callbackControlID != null)  (this._request.HttpVerb == HttpVerb.POST))
  {
   this._isCallback = true;
  }
  else if (!this.IsCrossPagePostBack)
  {
   VirtualPath path = null;
   if (this._requestValueCollection["__PREVIOUSPAGE"] != null)
   {
   try
   {
    path = VirtualPath.CreateNonRelativeAllowNull(DecryptString(this._requestValueCollection["__PREVIOUSPAGE"], Purpose.WebForms_Page_PreviousPageID));
   }
   catch
   {
    this._pageFlags[8] = true;
   }
   if ((path != null)  (path != this.Request.CurrentExecutionFilePathObject))
   {
    this._pageFlags[8] = true;
    this._previousPagePath = path;
   }
   }
  }
  }
  if (this.MaintainScrollPositionOnPostBack)
  {
  this.LoadScrollPosition();
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin PreInit");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_ENTER, this._context.WorkerRequest);
  }
  this.PerformPreInit();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_INIT_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End PreInit");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin Init");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_ENTER, this._context.WorkerRequest);
  }
  this.InitRecursive(null);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_INIT_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End Init");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin InitComplete");
  }
  this.OnInitComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End InitComplete");
  }
  if (this.IsPostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin LoadState");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_ENTER, this._context.WorkerRequest);
  }
  this.LoadAllState();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_VIEWSTATE_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End LoadState");
   this.Trace.Write("aspx.page", "Begin ProcessPostData");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_ENTER, this._context.WorkerRequest);
  }
  this.ProcessPostData(this._requestValueCollection, true);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_POSTDATA_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End ProcessPostData");
  }
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin PreLoad");
  }
  this.OnPreLoad(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End PreLoad");
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin Load");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_ENTER, this._context.WorkerRequest);
  }
  this.LoadRecursive();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
  EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_LOAD_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End Load");
  }
  if (this.IsPostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin ProcessPostData Second Try");
  }
  this.ProcessPostData(this._leftoverPostData, false);
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End ProcessPostData Second Try");
   this.Trace.Write("aspx.page", "Begin Raise ChangedEvents");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_ENTER, this._context.WorkerRequest);
  }
  this.RaiseChangedEvents();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_POST_DATA_CHANGED_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Raise ChangedEvents");
   this.Trace.Write("aspx.page", "Begin Raise PostBackEvent");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_ENTER, this._context.WorkerRequest);
  }
  this.RaisePostBackEvent(this._requestValueCollection);
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RAISE_POSTBACK_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Raise PostBackEvent");
  }
  }
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "Begin LoadComplete");
  }
  this.OnLoadComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
  this.Trace.Write("aspx.page", "End LoadComplete");
  }
  if (this.IsPostBack  this.IsCallback)
  {
  this.PrepareCallback(callbackControlID);
  }
  else if (!this.IsCrossPagePostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin PreRender");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_ENTER, this._context.WorkerRequest);
  }
  this.PreRenderRecursiveInternal();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_PRE_RENDER_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End PreRender");
  }
  }
 }
 if ((this._legacyAsyncInfo == null) || this._legacyAsyncInfo.CallerIsBlocking)
 {
  this.ExecuteRegisteredAsyncTasks();
 }
 this.ValidateRawUrlIfRequired();
 if (includeStagesAfterAsyncPoint)
 {
  if (this.IsCallback)
  {
  this.RenderCallback();
  }
  else if (!this.IsCrossPagePostBack)
  {
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "Begin PreRenderComplete");
  }
  this.PerformPreRenderComplete();
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End PreRenderComplete");
  }
  if (context.TraceIsEnabled)
  {
   this.BuildPageProfileTree(this.EnableViewState);
   this.Trace.Write("aspx.page", "Begin SaveState");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_ENTER, this._context.WorkerRequest);
  }
  this.SaveAllState();
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_SAVE_VIEWSTATE_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End SaveState");
   this.Trace.Write("aspx.page", "Begin SaveStateComplete");
  }
  this.OnSaveStateComplete(EventArgs.Empty);
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End SaveStateComplete");
   this.Trace.Write("aspx.page", "Begin Render");
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_ENTER, this._context.WorkerRequest);
  }
  if (str != null)
  {
   this.ExportWebPart(str);
  }
  else
  {
   this.RenderControl(this.CreateHtmlTextWriter(this.Response.Output));
  }
  if (EtwTrace.IsTraceEnabled(5, 4))
  {
   EtwTrace.Trace(EtwTraceType.ETW_TYPE_PAGE_RENDER_LEAVE, this._context.WorkerRequest);
  }
  if (context.TraceIsEnabled)
  {
   this.Trace.Write("aspx.page", "End Render");
  }
  this.CheckRemainingAsyncTasks(false);
  }
 }
 }
 catch (ThreadAbortException exception1)
 {
 HttpApplication.CancelModuleException exceptionState = exception1.ExceptionState as HttpApplication.CancelModuleException;
 if ((((includeStagesBeforeAsyncPoint  includeStagesAfterAsyncPoint)  (this._context.Handler == this))  ((this._context.ApplicationInstance != null)  (exceptionState != null)))  !exceptionState.Timeout)
 {
  this._context.ApplicationInstance.CompleteRequest();
  ThreadResetAbortWithAssert();
 }
 else
 {
  this.CheckRemainingAsyncTasks(true);
  throw;
 }
 }
 catch (ConfigurationException)
 {
 throw;
 }
 catch (Exception exception2)
 {
 PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_DURING_REQUEST);
 PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_TOTAL);
 if (!this.HandleError(exception2))
 {
  throw;
 }
 }
}

以上就是關(guān)于ASP.NET頁面生命周期的詳細(xì)內(nèi)容介紹，希望對(duì)大家的學(xué)習(xí)有所幫助。

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