IStateFormatter 介面

定義

命名空間:

System.Web.UI

組件:

System.Web.dll

定義型別為了將物件 Graph 序列化與還原序列化所實作的方法。

public interface class IStateFormatter

public interface IStateFormatter

type IStateFormatter = interface

Public Interface IStateFormatter

衍生

System.Web.UI.ObjectStateFormatter

範例

下列程式代碼範例示範如何建立 PageStatePersister 物件，以將檢視和控制狀態儲存至網頁伺服器上的數據流。 類別 StreamPageStatePersister 示範如何覆寫 Load 和 Save 方法來擷取及儲存頁面狀態資訊。 這些方法會使用 IStateFormatter 繼承自 類別的 PageStatePersister 介面來串行化和還原串行化檢視狀態。 此程式代碼範例是針對 類別提供的較大範例的 PageStatePersister 一部分。

namespace Samples.AspNet.CS
{

    using System;
    using System.IO;
    using System.Security.Permissions;
    using System.Web;
    using System.Web.UI;

    //
    // The StreamPageStatePersister is an example view state
    // persistence mechanism that persists view and control
    // state on the Web server.
    //
    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public class StreamPageStatePersister : PageStatePersister
    {

        public StreamPageStatePersister(Page page)
            : base(page)
        {
        }
        //
        // Load ViewState and ControlState.
        //
        public override void Load()
        {
            Stream stateStream = GetSecureStream();

            // Read the state string, using the StateFormatter.
            StreamReader reader = new StreamReader(stateStream);

            IStateFormatter formatter = this.StateFormatter;
            string fileContents = reader.ReadToEnd();

            // Deserilize returns the Pair object that is serialized in
            // the Save method.
            Pair statePair = (Pair)formatter.Deserialize(fileContents);

            ViewState = statePair.First;
            ControlState = statePair.Second;
            reader.Close();
            stateStream.Close();
        }
        //
        // Persist any ViewState and ControlState.
        //
        public override void Save()
        {

            if (ViewState != null || ControlState != null)
            {
                if (Page.Session != null)
                {
                    Stream stateStream = GetSecureStream();

                    StreamWriter writer = new StreamWriter(stateStream);

                    IStateFormatter formatter = this.StateFormatter;
                    Pair statePair = new Pair(ViewState, ControlState);

                    // Serialize the statePair object to a string.
                    string serializedState = formatter.Serialize(statePair);

                    writer.Write(serializedState);
                    writer.Close();
                    stateStream.Close();
                }
                else
                {
                    throw new InvalidOperationException("Session needed for StreamPageStatePersister.");
                }
            }
        }
        // Return a secure Stream for your environment.
        private Stream GetSecureStream()
        {
            // You must provide the implementation to build
            // a secure Stream for your environment.
            return null;
        }
    }
}

Imports System.IO
Imports System.Security.Permissions
Imports System.Web
Imports System.Web.UI

Namespace Samples.AspNet.VB

    ' The StreamPageStatePersister is an example view state
    ' persistence mechanism that persists view and control
    ' state on the Web server.
    '
    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public Class StreamPageStatePersister
        Inherits PageStatePersister


        Public Sub New(ByVal page As Page)
            MyBase.New(page)
        End Sub

        '
        ' Load ViewState and ControlState.
        '
        Public Overrides Sub Load()

            Dim stateStream As Stream
            stateStream = GetSecureStream()

            ' Read the state string, using the StateFormatter.
            Dim reader As New StreamReader(stateStream)

            Dim serializedStatePair As String
            serializedStatePair = reader.ReadToEnd
            Dim statePair As Pair

            Dim formatter As IStateFormatter
            formatter = Me.StateFormatter

            ' Deserilize returns the Pair object that is serialized in
            ' the Save method.      
            statePair = CType(formatter.Deserialize(serializedStatePair), Pair)

            ViewState = statePair.First
            ControlState = statePair.Second
            reader.Close()
            stateStream.Close()
        End Sub

        '
        ' Persist any ViewState and ControlState.
        '
        Public Overrides Sub Save()

            If Not (ViewState Is Nothing) OrElse Not (ControlState Is Nothing) Then
                If Not (Page.Session Is Nothing) Then

                    Dim stateStream As Stream
                    stateStream = GetSecureStream()

                    ' Write a state string, using the StateFormatter.
                    Dim writer As New StreamWriter(stateStream)

                    Dim formatter As IStateFormatter
                    formatter = Me.StateFormatter

                    Dim statePair As New Pair(ViewState, ControlState)

                    Dim serializedState As String
                    serializedState = formatter.Serialize(statePair)

                    writer.Write(serializedState)
                    writer.Close()
                    stateStream.Close()
                Else
                    Throw New InvalidOperationException("Session needed for StreamPageStatePersister.")
                End If
            End If
        End Sub
        ' Return a secure Stream for your environment.
        Private Function GetSecureStream() As Stream
            ' You must provide the implementation to build
            ' a secure Stream for your environment.
            Return Nothing
        End Function
    End Class
End Namespace

備註

介面 IStateFormatter 會定義類型可以實作的方法，以串行化和還原串行化 ASP.NET 網頁伺服器控件在其 屬性中 ViewState 維護的狀態。 衍生自 類別的 PageStatePersister 類別會使用此基礎結構來維護要求之間的 ASP.NET 頁面狀態。 根據預設，ASP.NET 頁面狀態是由 類別的 ObjectStateFormatter 實例串行化和還原串行化;不過，月臺和配接器開發人員可以在自己的類型上實 IStateFormatter 作介面來執行這項工作。

如需 Web 伺服器控制項狀態管理和檢視狀態的詳細資訊，請參閱 ASP.NET 狀態管理概觀 和 動態 Web 伺服器控制項和檢視狀態。

方法

Deserialize(String)	將已序列化成字串形式的物件狀態圖還原序列化。
Serialize(Object)	將 ASP.NET Web 伺服器控制項狀態序列化成字串的形式。

另請參閱

• PageStatePersister
• LosFormatter
• ObjectStateFormatter