两个粒度看Asp.net生命周期

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对于Asp.net页面层开发无论是写页面还是写控件，我觉得都可以用一句话描述:"Do the right thing at the right time in the right place."这是07年底的一篇东西，还是有点价值整理出来与大家共享。

本文从两个粒度对Asp.net生命周期做了展示，一是通过记录页面事件的触发顺序看请求的处理流程，一是通过Reflector看Page类内部对请求处理的实现，为了清晰我清理掉了ETW相关的代码保留了一个简化却足可以说明问题的流程骨架；

本文覆盖以下内容：

页面事件的触发顺序展示
清理掉ETW代码后的，Page类内部对请求处理的实现
MSDN关于Asp.net生命周期非常重要的四个表格
演示源代码下载

1using System;
2using System.Configuration;
3using System.Data;
4using System.Web;
5using System.Web.Security;
6using System.Web.UI;
7using System.Web.UI.HtmlControls;
8using System.Web.UI.WebControls;
9using System.Web.UI.WebControls.WebParts;
10
11public partial class _Default : System.Web.UI.Page
12

运行结果：

Page_PreInit

Page_Init

Page_InitComplete

Page_PreLoad

Page_Load

Page_LoadComplete

Page_PreRender

Page_SaveStateComplete

点击页面的Button后的输出：

Page_PreInit

Page_Init

Page_InitComplete

Page_PreLoad

Page_Load

Button事件触发！

Page_LoadComplete

Page_PreRender

Page_SaveStateComplete

我们从一个更细的粒度，在Reflector中看Page对请求处理的代码：

  1 private void ProcessRequestMain(bool includeStagesBeforeAsyncPoint, bool includeStagesAfterAsyncPoint)
  2 {
  3     try
  4     {
  5         HttpContext context = this.Context;
  6         string str = null;
  7         if (includeStagesBeforeAsyncPoint)
  8         {
  9             if (this.IsInAspCompatMode)
10             {
11                 AspCompatApplicationStep.OnPageStartSessionObjects();
12             }
13             if (this.PageAdapter != null)
14             {
15                 this._requestValueCollection = this.PageAdapter.DeterminePostBackMode();
16             }
17             else
18             {
19                 this._requestValueCollection = this.DeterminePostBackMode();
20             }
21             string callbackControlID = string.Empty;
22             if (this.DetermineIsExportingWebPart())
23             {
24                 if (!RuntimeConfig.GetAppConfig().WebParts.EnableExport)
25                 {
26                     throw new InvalidOperationException(SR.GetString("WebPartExportHandler_DisabledExportHandler"));
27                 }
28                 str = this.Request.QueryString["webPart"];
29                 if (string.IsNullOrEmpty(str))
30                 {
31                     throw new InvalidOperationException(SR.GetString("WebPartExportHandler_InvalidArgument"));
32                 }
33                 if (string.Equals(this.Request.QueryString["scope"], "shared", StringComparison.OrdinalIgnoreCase))
34                 {
35                     this._pageFlags.Set(4);
36                 }
37                 string str3 = this.Request.QueryString["query"];
38                 if (str3 == null)
39                 {
40                     str3 = string.Empty;
41                 }
42                 this.Request.QueryStringText = str3;
43                 context.Trace.IsEnabled = false;
44             }
45             if (this._requestValueCollection != null)
46             {
47                 if (this._requestValueCollection["__VIEWSTATEENCRYPTED"] != null)
48                 {
49                     this.ContainsEncryptedViewState = true;
50                 }
51                 callbackControlID = this._requestValueCollection["__CALLBACKID"];
52                 if ((callbackControlID != null) && (this._request.HttpVerb == HttpVerb.POST))
53                 {
54                     this._isCallback = true;
55                 }
56                 else if (!this.IsCrossPagePostBack)
57                 {
58                     VirtualPath path = null;
59                     if (this._requestValueCollection["__PREVIOUSPAGE"] != null)
60                     {
61                         try
62                         {
63                             path = VirtualPath.CreateNonRelativeAllowNull(DecryptString(this.        _requestValueCollection["__PREVIOUSPAGE"]));
64                         }
65                         catch (CryptographicException)
66                         {
67                             this._pageFlags[8] = true;
68                         }
69                         if ((path != null) && (path != this.Request.CurrentExecutionFilePathObject))
70                         {
71                             this._pageFlags[8] = true;
72                             this._previousPagePath = path;
73                         }
74                     }
75                 }
76             }
77             if (this.MaintainScrollPositionOnPostBack)
78             {
79                 this.LoadScrollPosition();
80             }
81
82             this.PerformPreInit();
83
84             this.InitRecursive(null);
85
86             this.OnInitComplete(EventArgs.Empty);
87
88             if (this.IsPostBack)
89             {
90                 this.LoadAllState();
91
92                 this.ProcessPostData(this._requestValueCollection, true);
93
94             }
95
96
97             this.OnPreLoad(EventArgs.Empty);
98
99             this.LoadRecursive();
100
101             if (this.IsPostBack)
102             {
103                 this.ProcessPostData(this._leftoverPostData, false);
104
105                 this.RaiseChangedEvents();
106
107                 this.RaisePostBackEvent(this._requestValueCollection);
108
109             }
110
111             this.OnLoadComplete(EventArgs.Empty);
112
113             if (this.IsPostBack && this.IsCallback)
114             {
115                 this.PrepareCallback(callbackControlID);
116             }
117             else if (!this.IsCrossPagePostBack)
118             {
119
120                 this.PreRenderRecursiveInternal();
121              }
122         }
123         if ((this._asyncInfo == null) || this._asyncInfo.CallerIsBlocking)
124         {
125             this.ExecuteRegisteredAsyncTasks();
126         }
127         if (includeStagesAfterAsyncPoint)
128         {
129             if (this.IsCallback)
130             {
131                 this.RenderCallback();
132             }
133             else if (!this.IsCrossPagePostBack)
134             {
135                 this.PerformPreRenderComplete();
136
137                 if (context.TraceIsEnabled)
138                 {
139                     this.BuildPageProfileTree(this.EnableViewState);
140                     this.Trace.Write("aspx.page", "Begin SaveState");
141                 }
142
143                 this.SaveAllState();
144
145                 this.OnSaveStateComplete(EventArgs.Empty);
146                 if (str != null)
147                 {
148                     this.ExportWebPart(str);
149                 }
150                 else
151                 {
152                     this.RenderControl(this.CreateHtmlTextWriter(this.Response.Output));
153                 }
154
155                 this.CheckRemainingAsyncTasks(false);
156             }
157         }
158     }
159     catch (ThreadAbortException exception)
160     {
161         HttpApplication.CancelModuleException exceptionState = exception.ExceptionState as HttpApplication.CancelModuleException;
162         if (((!includeStagesBeforeAsyncPoint || !includeStagesAfterAsyncPoint) || ((this._context.Handler != this) || (this._context.ApplicationInstance == null))) || ((exceptionState == null) || exceptionState.Timeout))
163         {
164             this.CheckRemainingAsyncTasks(true);
165             throw;
166         }
167         this._context.ApplicationInstance.CompleteRequest();
168         Thread.ResetAbort();
169     }
170     catch (ConfigurationException)
171     {
172         throw;
173     }
174     catch (Exception exception3)
175     {
176         PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_DURING_REQUEST);
177         PerfCounters.IncrementCounter(AppPerfCounter.ERRORS_TOTAL);
178         if (!this.HandleError(exception3))
179         {
180             throw;
181         }
182     }
183 }
184
185
186
187
188

private void PerformPreInit()
{
           this.OnPreInit(EventArgs.Empty);
    this.InitializeThemes();//看到主题和模板页是什么时候加载了吧
    this.ApplyMasterPage();
    this._preInitWorkComplete = true;
}

MSDN上对Asp.net生命周期解释有非常重要的四个表格：

Stage	Description
Page request	The page request occurs before the page life cycle begins. When the page is requested by a user, ASP.NET determines whether the page needs to be parsed and compiled (therefore beginning the life of a page), or whether a cached version of the page can be sent in response without running the page.
Start	In the start step, page properties such as Request and Response are set. At this stage, the page also determines whether the request is a postback or a new request and sets the IsPostBack property. Additionally, during the start step, the page's UICulture property is set.
Page initialization	During page initialization, controls on the page are available and each control's UniqueID property is set. Any themes are also applied to the page. If the current request is a postback, the postback data has not yet been loaded and control property values have not been restored to the values from view state.
Load	During load, if the current request is a postback, control properties are loaded with information recovered from view state and control state.
Validation	During validation, the Validate method of all validator controls is called, which sets the IsValid property of individual validator controls and of the page.
Postback event handling	If the request is a postback, any event handlers are called.
Rendering	Before rendering, view state is saved for the page and all controls. During the rendering phase, the page calls the Render method for each control, providing a text writer that writes its output to the OutputStream of the page's Response property.
Unload	Unload is called after the page has been fully rendered, sent to the client, and is ready to be discarded. At this point, page properties such as Response and Request are unloaded and any cleanup is performed.