IStateFormatter 接口

定义

public interface class IStateFormatter

public interface IStateFormatter

type IStateFormatter = interface

Public Interface IStateFormatter

派生

System.Web.UI.ObjectStateFormatter

示例

下面的代码示例演示如何创建一个 PageStatePersister 对象，用于将视图和控制状态保存到 Web 服务器上的流。 类 StreamPageStatePersister 演示如何重写 Load 和 Save 方法来提取和保存页面状态信息。 这些方法使用 IStateFormatter 从 PageStatePersister 类继承的 接口来序列化和反序列化视图状态。 此代码示例是为 PageStatePersister 类提供的一个更大示例的一部分。

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

注解

接口 IStateFormatter 定义类型可以实现的方法，以序列化和反序列化 ASP.NET Web 服务器控件在其 ViewState 属性中保持的状态。 派生自 PageStatePersister 类的类使用此基础结构来维护请求之间 ASP.NET 页的状态。 默认情况下，ASP.NET 页状态由 类的 ObjectStateFormatter 实例进行序列化和反序列化;但是，站点和适配器开发人员可以在自己的类型上实现 IStateFormatter 接口，以执行此操作。

有关 Web 服务器控件状态管理和视图状态的详细信息，请参阅 ASP.NET 状态管理概述 和 动态 Web 服务器控件和视图状态。

方法

适用于

另请参阅

• PageStatePersister
• LosFormatter
• ObjectStateFormatter