Page对象在SaveState阶段都做了什么？
当页面运行至SaveState阶段时，将调用其自身SaveAllState()方法，在这个方法内部，做了两件事，第一件事就是保存控件状态，即ControlState，第二件事就是保存控件视图状态，即ViewState。ControlState我们放到以后再说，今天说说ViewState，在SaveAllState()这个方法内部，调用控件的SaveViewStateRecursive()方法，在这个方法的内部，调用控件的SaveViewState方法，下面列出该方法的源码:
1
// Answer any state this control or its descendants want to save on freeze.
2 // The format for saving is Triplet(myState, ArrayList childIDs, ArrayList childStates),
3 // where myState or childStates and childIDs may be null.
4
internal object SaveViewStateRecursive() {
5
if (flags[disableViewState])
6 return null;
7
8 object adapterState = null;
9
if (_adapter != null) {
10 adapterState = _adapter.SaveAdapterViewState();
11
}
12
13 object controlSavedState = SaveViewState();
14
15 ArrayList childStates = null;
16 if (HasControls()) {
17 ControlCollection occasionalFieldControls = _occasionalFields.Controls;
18 int occasionalFieldControlCount = occasionalFieldControls.Count;
19
20 bool useId = LoadViewStateByID;
21 for (int i = 0; i < occasionalFieldControlCount; i++) {
22 Control child = occasionalFieldControls[i];
23 object childState = child.SaveViewStateRecursive();
24 if (childState != null) {
25 if (childStates == null) {
26 childStates = new ArrayList(occasionalFieldControlCount);
27 }
28
29 if (useId) {
30 child.EnsureID();
31 childStates.Add(child.ID);
32 }
33 else {
34 childStates.Add(i);
35 }
36 childStates.Add(childState);
37 }
38 }
39 }
40
41 if (_adapter != null) {
42 if ((controlSavedState != null) || (adapterState != null) || (childStates != null)) {
43 return new Triplet(controlSavedState, adapterState, childStates);
44 }
45 }
46 else {
47 if ((controlSavedState != null) || (childStates != null)) {
48 return new Pair(controlSavedState, childStates);
49 }
50 }
51
52 return null;
53
}
// Answer any state this control or its descendants want to save on freeze.2
// The format for saving is Triplet(myState, ArrayList childIDs, ArrayList childStates),3
// where myState or childStates and childIDs may be null.4
internal object SaveViewStateRecursive() { 
5
if (flags[disableViewState])6
return null; 7
8
object adapterState = null;9
if (_adapter != null) { 
10
adapterState = _adapter.SaveAdapterViewState();11
}12
13
object controlSavedState = SaveViewState(); 14
15
ArrayList childStates = null; 16
if (HasControls()) { 17
ControlCollection occasionalFieldControls = _occasionalFields.Controls;18
int occasionalFieldControlCount = occasionalFieldControls.Count; 19
20
bool useId = LoadViewStateByID;21
for (int i = 0; i < occasionalFieldControlCount; i++) {22
Control child = occasionalFieldControls[i]; 23
object childState = child.SaveViewStateRecursive();24
if (childState != null) { 25
if (childStates == null) { 26
childStates = new ArrayList(occasionalFieldControlCount);27
} 28
29
if (useId) {30
child.EnsureID();31
childStates.Add(child.ID); 32
}33
else { 34
childStates.Add(i); 35
}36
childStates.Add(childState); 37
}38
}39
}40
41
if (_adapter != null) {42
if ((controlSavedState != null) || (adapterState != null) || (childStates != null)) { 43
return new Triplet(controlSavedState, adapterState, childStates); 44
}45
} 46
else {47
if ((controlSavedState != null) || (childStates != null)) {48
return new Pair(controlSavedState, childStates);49
} 50
}51
52
return null; 53
}第5行代码，需要引起我们的注意，flags[disableViewState]和控件的EnableViewState属性想对应。
下边用一个简单的示例，来描述一下页面是如何递归保存其内部控件的视图状态：
Code上边的代码列出了一个简单页面和其对应的cs页面代码。
这个页面对应的控件树为：
下边列出Page、HtmlForm、Literal这三个主要对象的顺序图:
