對于Asp.net頁面層開發無論是寫頁面還是寫控件，我覺得都可以用一句話描述:"Do the right thing at the right time in the right place."這是07年底的一篇東西，還是有點價值整理出來與大家共享。
本文從兩個粒度對Asp.net生命周期做了展示，一是通過記錄頁面事件的觸發順序看請求的處理流程，一是通過Reflector看Page類内部對請求處理的實作，為了清晰我清理掉了ETW相關的代碼保留了一個簡化卻足可以說明問題的流程骨架；
本文覆寫以下内容：
頁面事件的觸發順序展示
清理掉ETW代碼後的，Page類内部對請求處理的實作
MSDN關于Asp.net生命周期非常重要的四個表格
示範源代碼下載下傳
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using System;
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using System.Configuration;
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using System.Data;
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using System.Web;
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using System.Web.Security;
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using System.Web.UI;
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using System.Web.UI.HtmlControls;
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using System.Web.UI.WebControls;
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using System.Web.UI.WebControls.WebParts;
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public partial class _Default : System.Web.UI.Page
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{
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protected void Page_PreInit(object sender, EventArgs e)
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{
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Response.Write("Page_PreInit<br/>");
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}
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protected void Page_Init(object sender, EventArgs e)
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Response.Write("Page_Init<br/>");
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protected void Page_InitComplete(object sender, EventArgs e)
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Response.Write("Page_InitComplete<br/>");
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protected void Page_PreLoad(object sender, EventArgs e)
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Response.Write("Page_PreLoad<br/>");
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protected void Page_Load(object sender, EventArgs e)
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Response.Write("Page_Load<br/>");
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protected void Page_LoadComplete(object sender, EventArgs e)
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Response.Write("Page_LoadComplete<br/>");
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protected void Page_PreRender(object sender, EventArgs e)
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Response.Write("Page_PreRender<br/>");
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protected void Page_SaveStateComplete(object sender, EventArgs e)
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Response.Write("Page_SaveStateComplete<br/>");
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protected void Page_Unload(object sender, EventArgs e)
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int i = 0;
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i++;//這行代碼是用來設定斷點的，為什麼不用Response.Write？你說呢？
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protected void Button1_Click(object sender, EventArgs e)
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Label1.Text = "ControlEvent";
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Response.Write("Button事件觸發！<br/>");
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}
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運作結果：
Page_PreInit
Page_Init
Page_InitComplete
Page_PreLoad
Page_Load
Page_LoadComplete
Page_PreRender
Page_SaveStateComplete
點選頁面的Button後的輸出：
Button事件觸發！
我們從一個更細的粒度，在Reflector中看Page對請求處理的代碼：
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();
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84 this.InitRecursive(null);
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86 this.OnInitComplete(EventArgs.Empty);
87
88 if (this.IsPostBack)
89 {
90 this.LoadAllState();
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92 this.ProcessPostData(this._requestValueCollection, true);
93
94 }
95
96
97 this.OnPreLoad(EventArgs.Empty);
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99 this.LoadRecursive();
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101 if (this.IsPostBack)
102 {
103 this.ProcessPostData(this._leftoverPostData, false);
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105 this.RaiseChangedEvents();
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107 this.RaisePostBackEvent(this._requestValueCollection);
108
109 }
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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();
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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
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private void PerformPreInit()
this.OnPreInit(EventArgs.Empty);
this.InitializeThemes();//看到主題和模闆頁是什麼時候加載了吧
this.ApplyMasterPage();
this._preInitWorkComplete = true;
MSDN上對Asp.net生命周期解釋有非常重要的四個表格：
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.
Life-cycle Events
Page Event
Typical Use
PreInit
Use this event for the following:
Check the IsPostBack property to determine whether this is the first time the page is being processed.
Create or re-create dynamic controls.
Set a master page dynamically.
Set the Theme property dynamically.
Read or set profile property values.
Note:
If the request is a postback, the values of the controls have not yet been restored from view state. If you set a control property at this stage, its value might be overwritten in the next event.
Init
Raised after all controls have been initialized and any skin settings have been applied. Use this event to read or initialize control properties.
InitComplete
Raised by the Page object. Use this event for processing tasks that require all initialization be complete.
PreLoad
Use this event if you need to perform processing on your page or control before the Load event.
After the Page raises this event, it loads view state for itself and all controls, and then processes any postback data included with the Request instance.
The Page calls the OnLoad event method on the Page, then recursively does the same for each child control, which does the same for each of its child controls until the page and all controls are loaded.
Use the OnLoad event method to set properties in controls and establish database connections.
Control events
Use these events to handle specific control events, such as a Button control's Click event or a TextBox control's TextChanged event.
In a postback request, if the page contains validator controls, check the IsValid property of the Page and of individual validation controls before performing any processing.
LoadComplete
Use this event for tasks that require that all other controls on the page be loaded.
PreRender
Before this event occurs:
The Page object calls EnsureChildControls for each control and for the page.
The PreRender event occurs for each control on the page. Use the event to make final changes to the contents of the page or its controls.
SaveStateComplete
Before this event occurs, ViewState has been saved for the page and for all controls. Any changes to the page or controls at this point will be ignored.
Use this event perform tasks that require view state to be saved, but that do not make any changes to controls.
Render
This is not an event; instead, at this stage of processing, the Page object calls this method on each control. All ASP.NET Web server controls have a Render method that writes out the control's markup that is sent to the browser.
A user control (an .ascx file) automatically incorporates rendering, so you do not need to explicitly render the control in code.
This event occurs for each control and then for the page. In controls, use this event to do final cleanup for specific controls, such as closing control-specific database connections.
For the page itself, use this event to do final cleanup work, such as closing open files and database connections, or finishing up logging or other request-specific tasks.
During the unload stage, the page and its controls have been rendered, so you cannot make further changes to the response stream. If you attempt to call a method such as the Response.Write method, the page will throw an exception.
Data Binding Events for Data-Bound Controls
To help you understand the relationship between the page life cycle and data binding events, the following table lists data-related events in data-bound controls such as the GridView, DetailsView, and FormView controls.
Control Event
DataBinding
This event is raised by data-bound controls before the PreRender event of the containing control (or of the Page object) and marks the beginning of binding the control to the data.
Use this event to manually open database connections, if required. (The data source controls often make this unnecessary.)
RowCreated (GridView only) or ItemCreated (DataList, DetailsView, SiteMapPath, DataGrid, FormView, Repeater, and ListView controls)
Use this event to manipulate content that is not dependent on data binding. For example, at run time, you might programmatically add formatting to a header or footer row in a GridView control.
RowDataBound (GridView only) or ItemDataBound (DataList, SiteMapPath, DataGrid, Repeater, and ListView controls)
When this event occurs, data is available in the row or item, so you can format data or set the FilterExpression property on child data source controls for displaying related data within the row or item.
DataBound
This event marks the end of data-binding operations in a data-bound control. In a GridView control, data binding is complete for all rows and any child controls.
Use this event to format data bound content or to initiate data binding in other controls that depend on values from the current control's content. (For details, see "Catch-up Events for Added Controls" earlier in this topic.)
Login Control Events
The Login control can use settings in the Web.config file to manage membership authentication automatically. However, if your application requires you to customize how the control works, or if you want to understand how Login control events relate to the page life cycle, you can use the events listed in the following table.
LoggingIn
This event is raised during a postback, after the page's LoadComplete event has occurred. It marks the beginning of the login process.
Use this event for tasks that must occur prior to beginning the authentication process.
Authenticate
This event is raised after the LoggingIn event.
Use this event to override or enhance the default authentication behavior of a Login control.
LoggedIn
This event is raised after the user name and password have been authenticated.
Use this event to redirect to another page or to dynamically set the text in the control. This event does not occur if there is an error or if authentication fails.
LoginError
This event is raised if authentication was not successful.
Use this event to set text in the control that explains the problem or to direct the user to a different page.