IStateManager 介面
定義
定義任何類別必須實作以支援伺服器控制項之檢視狀態管理的屬性和方法。Defines the properties and methods any class must implement to support view state management for a server control.
public interface class IStateManager
public interface IStateManager
type IStateManager = interface
Public Interface IStateManager
- 衍生
範例
下列程式碼範例顯示的類別會IStateManager執行介面。The following code example shows a class that implements the IStateManager interface. 其中包含IsTrackingViewState屬性的執行LoadViewState和、 SaveViewState TrackViewState和方法。It includes implementations of the IsTrackingViewState property and the LoadViewState, SaveViewState, and TrackViewState methods.
// Create a class that implements IStateManager so that
// it can manage its own view state.
[AspNetHostingPermission(SecurityAction.Demand,
Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class MyItem : IStateManager
{
private string _message;
// The StateBag object that allows you to save
// and restore view-state information.
private StateBag _viewstate;
// The constructor for the MyItem class.
public MyItem(string mesg)
{
_message = mesg;
_viewstate = new StateBag();
_viewstate.Add("message", _message);
}
// Create a Message property that reads from and writes
// to view state. If the set accessor writes the message
// value to view state, the StateBag.SetItemDirty method
// is called, telling view state that the item has changed.
public string Message
{
get
{
return (string)_viewstate["message"];
}
set
{
_message = value;
_viewstate.SetItemDirty("message", true);
}
}
// Implement the LoadViewState method. If the saved view state
// exists, the view-state value is loaded to the MyItem control.
void IStateManager.LoadViewState(object savedState)
{
_message = (string)_viewstate["message"];
if (savedState != null)
((IStateManager)_viewstate).LoadViewState(savedState);
}
// Implement the SaveViewState method. If the StateBag
// that stores the MyItem class's view state contains
// a value for the message property and if the value
// has changed since the TrackViewState method was last
// called, all view state for this class is deleted,
// using the StateBag.Clear method,and the new value is added.
object IStateManager.SaveViewState()
{
// Check whether the message property exists in
// the ViewState property, and if it does, check
// whether it has changed since the most recent
// TrackViewState method call.
if (!((IDictionary)_viewstate).Contains("message") || _viewstate.IsItemDirty("message"))
{
_viewstate.Clear();
// Add the _message property to the StateBag.
_viewstate.Add("message", _message);
}
return ((IStateManager)_viewstate).SaveViewState();
}
// Implement the TrackViewState method for this class by
// calling the TrackViewState method of the class's private
// _viewstate property.
void IStateManager.TrackViewState()
{
((IStateManager)_viewstate).TrackViewState();
}
// Implement the IsTrackingViewState method for this class
// by calling the IsTrackingViewState method of the class's
// private _viewstate property.
bool IStateManager.IsTrackingViewState
{
get
{
return ((IStateManager)_viewstate).IsTrackingViewState;
}
}
// Create a function that iterates through the view-state
// values stored for this class and returns the
// results as a string.
public string EnumerateViewState()
{
string keyName, keyValue;
string result = String.Empty;
StateItem myStateItem;
IDictionaryEnumerator myDictionaryEnumerator = _viewstate.GetEnumerator();
while (myDictionaryEnumerator.MoveNext())
{
keyName = (string)myDictionaryEnumerator.Key;
myStateItem = (StateItem)myDictionaryEnumerator.Value;
keyValue = (string)myStateItem.Value;
result = result + "<br>ViewState[" + keyName + "] = " + keyValue;
}
return result;
}
}
' Create a class that implements IStateManager so that
' it can manage its own view state.
<AspNetHostingPermission(SecurityAction.Demand, _
Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class MyItem
Implements IStateManager
Private _message As String
' The StateBag object that allows you to save
' and restore view-state information.
Private _viewstate As StateBag
' The constructor for the MyItem class.
Public Sub New(ByVal mesg As String)
_message = mesg
_viewstate = New StateBag()
_viewstate.Add("message", _message)
End Sub
' Create a Message property that reads from and writes
' to view state. If the set accessor writes the message
' value to view state, the StateBag.SetItemDirty method
' is called, telling view state that the item has changed.
Public Property Message() As String
Get
Return CStr(_viewstate("message"))
End Get
Set(ByVal value As String)
_message = value
_viewstate.SetItemDirty("message", True)
End Set
End Property
' Implement the LoadViewState method. If the saved view state
' exists, the view-state value is loaded to the MyItem
' control.
Sub LoadViewState(ByVal savedState As Object) Implements IStateManager.LoadViewState
_message = CStr(_viewstate("message"))
If Not (savedState Is Nothing) Then
CType(_viewstate, IStateManager).LoadViewState(savedState)
End If
End Sub
' Implement the SaveViewState method. If the StateBag
' that stores the MyItem class's view state contains
' a value for the message property and if the value
' has changed since the TrackViewState method was last
' called, all view state for this class is deleted,
' using the StateBag.Clear method,and the new value is added.
Function SaveViewState() As Object Implements IStateManager.SaveViewState
' Check whether the message property exists in
' the ViewState property, and if it does, check
' whether it has changed since the most recent
' TrackViewState method call.
If Not CType(_viewstate, IDictionary).Contains("message") OrElse _viewstate.IsItemDirty("message") Then
_viewstate.Clear()
' Add the _message property to the StateBag.
_viewstate.Add("message", _message)
End If
Return CType(_viewstate, IStateManager).SaveViewState()
End Function 'IStateManager.SaveViewState
' Implement the TrackViewState method for this class by
' calling the TrackViewState method of the class's private
' _viewstate property.
Sub TrackViewState() Implements IStateManager.TrackViewState
CType(_viewstate, IStateManager).TrackViewState()
End Sub
' Implement the IsTrackingViewState method for this class
' by calling the IsTrackingViewState method of the class's
' private _viewstate property.
ReadOnly Property IsTrackingViewState() As Boolean Implements IStateManager.IsTrackingViewState
Get
Return CType(_viewstate, IStateManager).IsTrackingViewState
End Get
End Property
' Create a function that iterates through the view-state
' values stored for this class and returns the
' results as a string.
Public Function EnumerateViewState() As String
Dim keyName, keyValue As String
Dim result As String = [String].Empty
Dim myStateItem As StateItem
Dim myDictionaryEnumerator As IDictionaryEnumerator = _viewstate.GetEnumerator()
While myDictionaryEnumerator.MoveNext()
keyName = CStr(myDictionaryEnumerator.Key)
myStateItem = CType(myDictionaryEnumerator.Value, StateItem)
keyValue = CStr(myStateItem.Value)
result = result + "<br>ViewState[" + keyName + "] = " + keyValue
End While
Return result
End Function 'EnumerateViewState
End Class
備註
伺服器控制項的 view 狀態包含控制項屬性的累計值。A server control's view state comprises the cumulative values of the control's properties. 這個介面包含儲存和載入伺服器控制項之 view 狀態值的方法, 以及指示控制項追蹤其 view 狀態變更的方法。This interface includes methods that save and load a server control's view state values, as well as a method that instructs the control to track any changes to its view state.
若要自訂 ASP.NET 應用程式管理伺服器控制項檢視狀態的方式, 您必須建立可執行此介面的類別, 因為您無法StateBag繼承自類別。To customize the way your ASP.NET application manages server control view state, you must create a class that implements this interface because you cannot inherit from the StateBag class.
屬性
IsTrackingViewState |
當類別實作時,取得值,表示伺服器控制項是否正追蹤其狀態變更。When implemented by a class, gets a value indicating whether a server control is tracking its view state changes. |
方法
LoadViewState(Object) |
當類別實作時,載入伺服器控制項預先儲存的檢視狀態到控制項。When implemented by a class, loads the server control's previously saved view state to the control. |
SaveViewState() |
當類別實作時,儲存伺服器控制項檢視狀態的變更至 Object。When implemented by a class, saves the changes to a server control's view state to an Object. |
TrackViewState() |
當類別實作時,指示伺服器控制項以追蹤其檢視狀態的變更。When implemented by a class, instructs the server control to track changes to its view state. |