Page对象在Init阶段递归调用其内部控件的TrackViewState()方法
我们知道，Page对象Init阶段，要调用Control.InitRecursive方法，这个方法的内部会递归调用其内部控件的TrackViewState()方法，我们先看看Control.InitRecursive方法的源码：
internal virtual void InitRecursive(Control namingContainer) {
ResolveAdapter();
if (_occasionalFields != null && _occasionalFields.Controls != null) { 
if (flags[isNamingContainer]) { namingContainer = this; 
} string oldmsg = _occasionalFields.Controls.SetCollectionReadOnly(SR.Parent_collections_readonly); int controlCount = _occasionalFields.Controls.Count; for (int i = 0; i < controlCount; i++) { Control control = _occasionalFields.Controls[i]; // Propagate the page and namingContainer control.UpdateNamingContainer(namingContainer); if ((control._id == null) && (namingContainer != null) && !control.flags[idNotRequired]) { control.GenerateAutomaticID(); } control._page = Page; control.InitRecursive(namingContainer); } _occasionalFields.Controls.SetCollectionReadOnly(oldmsg); } // Only make the actual call if it hasn't already happened (ASURT 111303) if (_controlState < ControlState.Initialized) { _controlState = ControlState.ChildrenInitialized; // framework also initialized if ((Page != null) && !DesignMode) { if (Page.ContainsTheme && EnableTheming) { ApplySkin(Page); } } if (_adapter != null) { _adapter.OnInit(EventArgs.Empty); } else { OnInit(EventArgs.Empty); } _controlState = ControlState.Initialized; } // track all subsequent state changes TrackViewState(); #if DEBUG ControlInvariant(); #endif
} /// <devdoc> /// <para>Turns on tracking of view state changes to the control /// so that they can be stored in the <see langword='StateBag'/> /// object.</para> /// </devdoc> protected virtual void TrackViewState() { if (_viewState != null) _viewState.TrackViewState(); flags.Set(marked); } 下边我用一个简单的示例，来表示一下这个过程：
1
Code
2<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
3
4<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
5<html xmlns="http://www.w3.org/1999/xhtml">
6<head runat="server">
7 <title>无标题页</title>
8</head>
9<body>
10 <form id="form1" runat="server">
11 <div>
12 <asp:Literal ID="Literal1" runat="server"></asp:Literal></div>
13 </form>
14</body>
15</html>
Code2
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>3
4
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">5
<html xmlns="http://www.w3.org/1999/xhtml">6
<head runat="server">7
<title>无标题页</title>8
</head>9
<body>10
<form id="form1" runat="server">11
<div>12
<asp:Literal ID="Literal1" runat="server"></asp:Literal></div>13
</form>14
</body>15
</html>上边是一段简单的代码，下边用顺序图的方式来说明一下这段代码的主要对象(Page,HtmlForm,Literal)是如何递归调用子控件的TrackViewState（）方法：
