IStateManager Интерфейс

Определение

Определяет свойства и методы, которые должны быть реализованы любым классом для поддержки управления состоянием отображения для серверного элемента управления.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
Производный

Примеры

В следующем примере кода показан класс, реализующий IStateManager интерфейс.The following code example shows a class that implements the IStateManager interface. Он включает реализации IsTrackingViewState свойства LoadViewStateи методы, SaveViewStateи TrackViewState .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

Комментарии

Состояние представления серверного элемента управления состоит из совокупных значений свойств элемента управления.A server control's view state comprises the cumulative values of the control's properties. Этот интерфейс включает методы, которые сохраняют и загружают значения состояния представления серверного элемента управления, а также метод, который сообщает элементу управления о необходимости отслеживания изменений в состоянии представления.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.

Чтобы настроить способ, которым приложение ASP.NET управляет состоянием представления серверного элемента управления, необходимо создать класс, реализующий этот интерфейс, так как наследование от StateBag класса невозможно.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.

Свойства

IsTrackingViewState

При реализации каким-либо классом, получает значение, указывающее, на отслеживание изменений состояния просмотра серверным элементом управления.When implemented by a class, gets a value indicating whether a server control is tracking its view state changes.

Методы

LoadViewState(Object)

При реализации каким-либо классом, загружает в элемент управления ранее сохраненное состояние просмотра серверного элемента управления.When implemented by a class, loads the server control's previously saved view state to the control.

SaveViewState()

При реализации каким-либо классом сохраняет изменения состояния просмотра серверного элемента управления в Object.When implemented by a class, saves the changes to a server control's view state to an Object.

TrackViewState()

При реализации каким-либо классом, дает серверному элементу управления команду отслеживать изменения в состоянии просмотра.When implemented by a class, instructs the server control to track changes to its view state.

Применяется к

Дополнительно