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SessionStateUtility 类

NET Framework 类库 
SessionStateUtility 类 

注意：此类在 .NET Framework 2.0 版中是新增的。

提供会话状态模块和会话状态存储提供程序使用的帮助器方法，用于管理 ASP.NET 应用程序的会话信息。无法继承此类。

命名空间:System.Web.SessionState
程序集:System.Web（在 system.web.dll 中）

语法
Visual Basic（声明）
Public NotInheritable Class SessionStateUtility
Visual Basic（用法）
可对静态类的成员直接进行访问，无需类的实例。
C#
public static class SessionStateUtility
C++
public ref class SessionStateUtility abstract sealed
J#
public final class SessionStateUtility
JScript
public final class SessionStateUtility
备注

SessionStateUtility 类提供会话状态模块或会话状态存储提供程序使用的静态帮助器方法，应用程序开发人员不必从代码中调用这些方法。

下表描述了会话状态模块和会话状态存储提供程序如何使用这些方法。

 

方法

使用

GetHttpSessionStateFromContext 方法

自定义会话状态模块可以用来检索现有会话的会话信息，或创建新会话的会话信息。

AddHttpSessionStateToContext 方法

由会话状态模块调用，以向当前 HttpContext 添加会话数据，并通过 Session 属性使之可用于应用程序代码。

RemoveHttpSessionStateFromContext 方法

在请求结束和处理 ReleaseRequestState 或 EndRequest 事件时由会话状态模块调用，以清除当前 HttpContext 中的会话数据。

GetSessionStaticObjects 方法

由会话状态模块调用，根据 Global.asax 文件定义的对象引用 StaticObjects 集合。返回的 HttpStaticObjectsCollection 集合与添加到当前 HttpContext 的会话数据一起提供。

会话数据作为 HttpSessionStateContainer 对象或任何有效的 IHttpSessionState 接口实现传递到当前 HttpContext，或从中检索。

有关实现会话状态存储提供程序的信息，请参见 实现会话状态存储提供程序。

示例

下面的代码示例演示了一个自定义会话状态模块实现，它使用 Hashtable 将会话信息存储到内存中。该模块使用 SessionStateUtility 类引用当前的 HttpContext 和 SessionIDManager，检索当前的 HttpStaticObjectsCollection，并引发 ASP.NET 应用程序 Global.asax 文件中定义的 Session_OnEnd 事件。该应用程序无法防止并发的 Web 请求使用相同的会话标识符。

Visual Basic 复制到剪贴板
Imports System
Imports System.Web
Imports System.Web.SessionState
Imports System.Collections
Imports System.Threading
Imports System.Web.Configuration
Imports System.Configuration
Namespace Samples.AspNet.SessionState
Public NotInheritable Class MySessionStateModule
Implements IHttpModule
Private pSessionItems  As Hashtable        = New Hashtable()
Private pTimer         As Timer
Private pTimerSeconds  As Integer          = 10
Private pInitialized   As Boolean          = False
Private pTimeout       As Integer
Private pCookieMode    As HttpCookieMode   = HttpCookieMode.UseCookies
Private pHashtableLock As ReaderWriterLock = New ReaderWriterLock()
Private pSessionIDManager As ISessionIDManager
Private pSessionID        As String
Private pConfig           As SessionStateSection
' The SessionItem class is used to store data for a particular session along with
' an expiration date and time. SessionItem objects are added to the local Hashtable
' in the OnReleaseRequestState event handler and retrieved from the local Hashtable
' in the OnAcquireRequestState event handler. The ExpireCallback method is called
' periodically by the local Timer to check for all expired SessionItem objects in the
' local Hashtable and remove them.
Private pSessionData As SessionItem
Class SessionItem
Friend Items         As SessionStateItemCollection
Friend StaticObjects As HttpStaticObjectsCollection
Friend Expires       As DateTime
End Class
'
' IHttpModule.Init
'
Public Sub Init(app As HttpApplication) Implements IHttpModule.Init
' Add event handlers.
AddHandler app.AcquireRequestState, New EventHandler(AddressOf Me.OnAcquireRequestState)
AddHandler app.ReleaseRequestState, New EventHandler(AddressOf Me.OnReleaseRequestState)
' Get a reference to the SessionIDManager for the current HttpApplication.
pSessionIDManager = new SessionIDManager()
PSessioNIDManager.Initialize()
' If not already initialized, initialize timer and configuration.
If Not pInitialized Then
SyncLock Me
If Not pInitialized Then
' Create a Timer to invoke the ExpireCallback method based on
' the pTimerSeconds value (e.g. every 10 seconds).
pTimer = New Timer(New TimerCallback(AddressOf Me.ExpireCallback), _
Nothing, _
0, _
pTimerSeconds*1000)
' Get the configuration section and set timeout and CookieMode values.
Dim cfg As System.Configuration.Configuration = _
WebConfigurationManager.OpenWebConfiguration( _
System.Web.Hosting.HostingEnvironment.ApplicationVirtualPath)
pConfig = CType(cfg.GetSection("system.web/sessionState"), SessionStateSection)
pTimeout = CInt(pConfig.Timeout.TotalMinutes)
pCookieMode = pConfig.Cookieless
pInitialized = True
End If
End SyncLock
End If
End Sub
'
' IHttpModule.Dispose
'
Public Sub Dispose() Implements IHttpModule.Dispose
If Not pTimer Is Nothing Then CType(pTimer, IDisposable).Dispose()
End Sub
'
' Called periodically by the Timer created in the Init method to check for 
' expired sessions and remove expired data.
'
Sub ExpireCallback(state As Object)
Try
pHashtableLock.AcquireWriterLock(Int32.MaxValue)
For Each entry As DictionaryEntry In pSessionItems
Dim item As SessionItem = CType(entry.Value, SessionItem)
If item.Expires <= DateTime.Now Then
pSessionItems.Remove(enTry.Key)
Dim stateProvider As HttpSessionStateContainer = _
New HttpSessionStateContainer(pSessionID, _
item.Items, _
item.StaticObjects, _
pTimeout, _
False, _
pCookieMode, _
SessionStateMode.Custom, _
False)
SessionStateUtility.RaiseSessionEnd(stateProvider, Me, EventArgs.Empty)
End If
Next
Finally
pHashtableLock.ReleaseWriterLock()
End Try
End Sub
'
' Event handler for HttpApplication.AcquireRequestState
'
Private Sub OnAcquireRequestState(source As Object, args As EventArgs)
Dim app     As HttpApplication = CType(source, HttpApplication)
Dim context As HttpContext     = app.Context
Dim isNew   As Boolean         = False
pSessionData = Nothing
pSessionID = pSessionIDManager.GetSessionID(context)
If Not pSessionID Is Nothing Then
Try
pHashtableLock.AcquireReaderLock(Int32.MaxValue)
pSessionData = CType(pSessionItems(pSessionID), SessionItem)
If Not pSessionData Is Nothing Then _
pSessionData.Expires = DateTime.Now.AddMinutes(pTimeout)
Finally
pHashtableLock.ReleaseReaderLock()
End Try
Else
Dim redirected, cookieAdded As Boolean
pSessionID = pSessionIDManager.CreateSessionID(context)
pSessionIDManager.SaveSessionID(context, pSessionID, redirected, cookieAdded)
If redirected Then Return
End If
If pSessionData Is Nothing Then
' Identify the session as a New session state instance. Create a New SessionItem
' and add it to the local Hashtable.
isNew = True
pSessionData = New SessionItem()
pSessionData.Items         = New SessionStateItemCollection()
pSessionData.StaticObjects = SessionStateUtility.GetSessionStaticObjects(context)
pSessionData.Expires       = DateTime.Now.AddMinutes(pTimeout)
Try
pHashtableLock.AcquireWriterLock(Int32.MaxValue)
pSessionItems(pSessionID) = pSessionData
Finally
pHashtableLock.ReleaseWriterLock()
End Try
End If
' Add the session data to the current HttpContext.
SessionStateUtility.AddHttpSessionStateToContext(context, _
New HttpSessionStateContainer(pSessionID, _
pSessionData.Items, _
pSessionData.StaticObjects, _
pTimeout, _
isNew, _
pCookieMode, _
SessionStateMode.Custom, _
False))
' Execute the Session_OnStart event for a New session.
If isNew Then RaiseEvent Start(Me, EventArgs.Empty)
End Sub
'
' Event for Session_OnStart event in the Global.asax file.
'
Public Event Start As EventHandler
'
' Event handler for HttpApplication.ReleaseRequestState
'
Private Sub OnReleaseRequestState(source As Object, args As EventArgs)
Dim app     As HttpApplication = CType(source, HttpApplication)
Dim context As HttpContext     = app.Context
' Read the session state from the context
Dim stateProvider As HttpSessionStateContainer =  _
CType(SessionStateUtility.GetHttpSessionStateFromContext(context), HttpSessionStateContainer)
' If Session.Abandon() was called, remove the session data from the local Hashtable
' and execute the Session_OnEnd event from the Global.asax file.
If stateProvider.IsAbandoned Then
Try
pHashtableLock.AcquireWriterLock(Int32.MaxValue)
pSessionItems.Remove(pSessionID)
Finally
pHashtableLock.ReleaseWriterLock()
End Try
SessionStateUtility.RaiseSessionEnd(stateProvider, Me, EventArgs.Empty)
End If
SessionStateUtility.RemoveHttpSessionStateFromContext(context)
End Sub
End Class
End Namespace
C# 复制到剪贴板
using System;
using System.Web;
using System.Web.SessionState;
using System.Collections;
using System.Threading;
using System.Web.Configuration;
using System.Configuration;
namespace Samples.AspNet.SessionState
{
public sealed class MySessionStateModule : IHttpModule
{
private Hashtable        pSessionItems    = new Hashtable();
private Timer            pTimer;
private int              pTimerSeconds    = 10;
private bool             pInitialized     = false;
private int              pTimeout;
private HttpCookieMode   pCookieMode      = HttpCookieMode.UseCookies;
private ReaderWriterLock pHashtableLock   = new ReaderWriterLock();
private ISessionIDManager   pSessionIDManager;
private string              pSessionID;
private SessionStateSection pConfig;
// The SessionItem class is used to store data for a particular session along with
// an expiration date and time. SessionItem objects are added to the local Hashtable
// in the OnReleaseRequestState event handler and retrieved from the local Hashtable
// in the OnAcquireRequestState event handler. The ExpireCallback method is called
// periodically by the local Timer to check for all expired SessionItem objects in the
// local Hashtable and remove them.
private SessionItem pSessionData;
class SessionItem
{
internal SessionStateItemCollection  Items;
internal HttpStaticObjectsCollection StaticObjects;
internal DateTime                    Expires;
}
//
// IHttpModule.Init
//
public void Init(HttpApplication app)
{
// Add event handlers.
app.AcquireRequestState += new EventHandler(this.OnAcquireRequestState);
app.ReleaseRequestState += new EventHandler(this.OnReleaseRequestState);
// Create a SessionIDManager.
pSessionIDManager = new SessionIDManager();
pSessionIDManager.Initialize();
// If not already initialized, initialize timer and configuration.
if (!pInitialized)
{
lock (typeof(MySessionStateModule))
{
if (!pInitialized)
{
// Create a Timer to invoke the ExpireCallback method based on
// the pTimerSeconds value (e.g. every 10 seconds).
pTimer = new Timer(new TimerCallback(this.ExpireCallback),
null,
0,
pTimerSeconds*1000);
// Get the configuration section and set timeout and CookieMode values.
Configuration cfg =
WebConfigurationManager.OpenWebConfiguration(System.Web.Hosting.HostingEnvironment.ApplicationVirtualPath);
pConfig = (SessionStateSection)cfg.GetSection("system.web/sessionState");
pTimeout = (int)pConfig.Timeout.TotalMinutes;
pCookieMode = pConfig.Cookieless;
pInitialized = true;
}
}
}
}
//
// IHttpModule.Dispose
//
public void Dispose()
{
if (pTimer != null)
((IDisposable)pTimer).Dispose();
}
//
// Called periodically by the Timer created in the Init method to check for 
// expired sessions and remove expired data.
//
void ExpireCallback(object state)
{
try
{
pHashtableLock.AcquireWriterLock(Int32.MaxValue);
foreach (DictionaryEntry entry in pSessionItems)
{
SessionItem item = (SessionItem)entry.Value;
if (item.Expires <= DateTime.Now)
{
pSessionItems.Remove(entry.Key);
HttpSessionStateContainer stateProvider =
new HttpSessionStateContainer(pSessionID,
item.Items,
item.StaticObjects,
pTimeout,
false,
pCookieMode,
SessionStateMode.Custom,
false);
SessionStateUtility.RaiseSessionEnd(stateProvider, this, EventArgs.Empty);
}
}
}
finally
{
pHashtableLock.ReleaseWriterLock();
}
}
//
// Event handler for HttpApplication.AcquireRequestState
//
private void OnAcquireRequestState(object source, EventArgs args)
{
HttpApplication app     = (HttpApplication)source;
HttpContext     context = app.Context;
bool            isNew   = false;
pSessionData = null;
pSessionID = pSessionIDManager.GetSessionID(context);
if (pSessionID != null)
{
try
{
pHashtableLock.AcquireReaderLock(Int32.MaxValue);
pSessionData = (SessionItem)pSessionItems[pSessionID];
if (pSessionData != null)
pSessionData.Expires = DateTime.Now.AddMinutes(pTimeout);
}
finally
{
pHashtableLock.ReleaseReaderLock();
}
}
else
{
bool redirected, cookieAdded;
pSessionID = pSessionIDManager.CreateSessionID(context);
pSessionIDManager.SaveSessionID(context, pSessionID, out redirected, out cookieAdded);
if (redirected)
return;
}
if (pSessionData == null)
{
// Identify the session as a new session state instance. Create a new SessionItem
// and add it to the local Hashtable.
isNew = true;
pSessionData = new SessionItem();
pSessionData.Items         = new SessionStateItemCollection();
pSessionData.StaticObjects = SessionStateUtility.GetSessionStaticObjects(context);
pSessionData.Expires       = DateTime.Now.AddMinutes(pTimeout);
try
{
pHashtableLock.AcquireWriterLock(Int32.MaxValue);
pSessionItems[pSessionID] = pSessionData;
}
finally
{
pHashtableLock.ReleaseWriterLock();
}
}
// Add the session data to the current HttpContext.
SessionStateUtility.AddHttpSessionStateToContext(context,
new HttpSessionStateContainer(pSessionID,
pSessionData.Items,
pSessionData.StaticObjects,
pTimeout,
isNew,
pCookieMode,
SessionStateMode.Custom,
false));
// Execute the Session_OnStart event for a new session.
if (isNew && Start != null)
{
Start(this, EventArgs.Empty);
}
}
//
// Event for Session_OnStart event in the Global.asax file.
//
public event EventHandler Start;
//
// Event handler for HttpApplication.ReleaseRequestState
//
private void OnReleaseRequestState(object source, EventArgs args)
{
HttpApplication app     = (HttpApplication)source;
HttpContext     context = app.Context;
// Read the session state from the context
HttpSessionStateContainer stateProvider =
(HttpSessionStateContainer)(SessionStateUtility.GetHttpSessionStateFromContext(context));
// If Session.Abandon() was called, remove the session data from the local Hashtable
// and execute the Session_OnEnd event from the Global.asax file.
if (stateProvider.IsAbandoned)
{
try
{
pHashtableLock.AcquireWriterLock(Int32.MaxValue);
pSessionItems.Remove(pSessionID);
}
finally
{
pHashtableLock.ReleaseWriterLock();
}
SessionStateUtility.RaiseSessionEnd(stateProvider, this, EventArgs.Empty);
}
SessionStateUtility.RemoveHttpSessionStateFromContext(context);
}
}
}

若要在 ASP.NET 应用程序中使用此自定义会话状态模块，您可以按以下示例，替换 Web.config 文件中现有的 SessionStateModule 引用。

<configuration>
<system.web>
<httpModules>
<remove name="Session" />
<add name="Session"
type="Samples.AspNet.SessionState.MySessionStateModule" />
</httpModules>
</system.web>
</configuration>
.NET Framework 安全性
继承层次结构
System.Object
  System.Web.SessionState.SessionStateUtility
线程安全
此类型的任何公共静态（Visual Basic 中的 Shared）成员都是线程安全的，但不保证所有实例成员都是线程安全的。
平台

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 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

版本信息

.NET Framework

受以下版本支持：2.0
请参见
posted @ 2006-06-03 23:47  工具人Kim哥  阅读(493)  评论(0)    收藏  举报
持续完善 Pinda.cn 秒建营销活动 通过低代码 零代码的模式快速创建营销活动，欢迎使用 。