IStateManager-Schnittstelle
Definiert die Eigenschaften und Methoden, die jede Klasse implementieren muss, um die Anzeigezustandsverwaltung eines Serversteuerelements zu unterstützen.
Namespace: System.Web.UI
Assembly: System.Web (in system.web.dll)
Syntax
'Declaration
Public Interface IStateManager
'Usage
Dim instance As IStateManager
public interface IStateManager
public interface class IStateManager
public interface IStateManager
public interface IStateManager
Hinweise
Der Anzeigezustand eines Serversteuerelements setzt sich aus den kumulativen Werten der Steuerelementeigenschaften zusammen. Diese Schnittstelle beinhaltet Methoden zum Laden und Speichern der Anzeigezustandswerte eines Serversteuerelements sowie eine Methode, mit der ein Steuerelement angewiesen wird, alle Änderungen des Anzeigezustands zu verfolgen.
Wenn Sie die Ansichtszustandsverwaltung für Serversteuerelemente in Ihrer ASP.NET-Anwendung anpassen möchten, müssen Sie eine Klasse zur Implementierung dieser Schnittstelle erstellen, da Sie die StateBag-Klasse nicht vererben können.
Beispiel
Im folgenden Codebeispiel wird eine Klasse veranschaulicht, die die IStateManager-Schnittstelle implementiert. Es enthält Implementierungen der IsTrackingViewState-Eigenschaft sowie der LoadViewState-Methode, der SaveViewState-Methode und der TrackViewState-Methode.
' 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 'New
' 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 'LoadViewState
' 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 'IStateManager.TrackViewState
' 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 'MyItem
// 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.
public class MyItem implements 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);
} //MyItem
// 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.
/** @property
*/
public String get_Message()
{
return (String)(_viewState.get_Item("message"));
} //get_Message
/** @property
*/
public void set_Message(String value)
{
_message = value;
_viewState.SetItemDirty("message", true);
} //set_Message
// Implement the LoadViewState method. If the saved view state
// exists, the view-state value is loaded to the MyItem control.
public void LoadViewState(Object savedState)
{
_message = (String)(_viewState.get_Item("message"));
if (savedState != null) {
((IStateManager)_viewState).LoadViewState(savedState);
}
} //LoadViewState
// 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.
public Object 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();
} //SaveViewState
// Implement the TrackViewState method for this class by
// calling the TrackViewState method of the class's private
// _viewState property.
public void TrackViewState()
{
((IStateManager)_viewState).TrackViewState();
} //TrackViewState
// Implement the IsTrackingViewState method for this class
// by calling the IsTrackingViewState method of the class's
// private _viewState property.
/** @property
*/
public boolean get_IsTrackingViewState()
{
return ((IStateManager)_viewState).get_IsTrackingViewState();
} // get_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 = "";
StateItem myStateItem;
IDictionaryEnumerator myDictionaryEnumerator =
_viewState.GetEnumerator();
while (myDictionaryEnumerator.MoveNext()) {
keyName = (String)myDictionaryEnumerator.get_Key();
myStateItem = (StateItem) myDictionaryEnumerator.get_Value();
keyValue = (String)myStateItem.get_Value();
result = result + "<br>ViewState[" + keyName + "] = " + keyValue;
}
return result;
} //EnumerateViewState
} //MyItem
Plattformen
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
Siehe auch
Referenz
IStateManager-Member
System.Web.UI-Namespace
StateBag
StateItem