Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / MIT / System / Web / UI / MobileControls / SessionViewState.cs / 1305376 / SessionViewState.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- using System; using System.Collections; using System.Diagnostics; using System.ComponentModel; using System.Globalization; using System.IO; using System.Runtime.Serialization; using System.Text; using System.Web; using System.Web.SessionState; using System.Web.Util; using System.Web.UI; using System.Security.Permissions; namespace System.Web.UI.MobileControls { /* * Session-based view state. * * When saving view state on the server as session data, some critical problems * arise. The core issue behind most of these is how to handle the user * clicking the Back button. When the user does this, there is no corresponding * notification to the server, and the client and server session state are thrown * out of [....]. * * This class attempts to alleviate this by storing a small history of view states * in session data. * * To save session view state, construct a new object, set the ViewState and ActiveForm * properties, and call Save. You'll get back a reference that contains the * state reference to write out. * * To load session view state, construct a new object, and call Load. The class will * attempt to construct the view state from its history. * * Copyright (c) 2000 Microsoft Corporation */ [Obsolete("The System.Web.Mobile.dll assembly has been deprecated and should no longer be used. For information about how to develop ASP.NET mobile applications, see http://go.microsoft.com/fwlink/?LinkId=157231.")] internal class SessionViewState { private static readonly String ViewStateKey = "ViewState"; private Object _state; internal SessionViewState() { } internal /*public*/ Object ViewState { get { return _state; } set { _state = value; } } internal /*public*/ Pair Save(MobilePage page) { SessionViewStateHistory history = (SessionViewStateHistory)page.Session[ViewStateKey]; if (history == null) { history = new SessionViewStateHistory(HttpContext.Current); page.Session[ViewStateKey] = history; } SessionViewStateHistoryItem historyItem = new SessionViewStateHistoryItem(); SaveTo(historyItem); #if TRACE historyItem.Url = page.Request.FilePath; #endif return history.Push(historyItem); } internal /*public*/ void Load(MobilePage page, Pair id) { _state = null; SessionViewStateHistory history = (SessionViewStateHistory)page.Session[ViewStateKey]; if (history != null) { SessionViewStateHistoryItem historyItem = history.Find(id); if (historyItem != null) { LoadFrom(historyItem); } } } private void SaveTo(SessionViewStateHistoryItem historyItem) { historyItem.ViewState = _state; } private void LoadFrom(SessionViewStateHistoryItem historyItem) { _state = historyItem.ViewState; } #if TRACE internal /*public*/ void Dump(MobilePage page, out ArrayList arr) { SessionViewStateHistory history; if ((page is IRequiresSessionState) && !(page is IReadOnlySessionState)) { history = (SessionViewStateHistory)page.Session[ViewStateKey]; } else { history = null; } if (history != null) { history.Dump(out arr); } else { arr = new ArrayList(); } } #endif [ Serializable ] private class SessionViewStateHistoryItem : ISerializable { #if TRACE public String Url; public String Id; #endif public Object ViewState; public SessionViewStateHistoryItem() { } public SessionViewStateHistoryItem(SerializationInfo info, StreamingContext context) { String s = (String)info.GetString("s"); if (s.Length > 0) { ViewState = new LosFormatter().Deserialize(s); } else { ViewState = null; } } [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter=true)] void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context) { if (ViewState != null) { StringWriter s = new StringWriter(CultureInfo.InvariantCulture); new LosFormatter().Serialize(s, ViewState); info.AddValue("s", s.ToString()); } else { info.AddValue("s", String.Empty); } } } // Session view state history. This is the history record kept in each session. [ Serializable ] private class SessionViewStateHistory { private int _historySize; private SessionViewStateHistoryItem[] _history; private int _currentHistoryIndex = 0; private int _historyUsed = 0; private DateTime _sessionUniqueID = DateTime.Now; private int _currentHistoryID = 0; public SessionViewStateHistory(HttpContext context) { _historySize = ControlsConfig.GetFromContext(context).SessionStateHistorySize; if (_historySize < 1) { throw new Exception( SR.GetString(SR.SessionViewState_InvalidSessionStateHistory)); } _history = new SessionViewStateHistoryItem[_historySize]; } public Pair Push(SessionViewStateHistoryItem item) { Pair id = new Pair(_sessionUniqueID, _currentHistoryID); _currentHistoryID++; _history[_currentHistoryIndex] = item; _currentHistoryIndex = (_currentHistoryIndex + 1) % _historySize; if (_historyUsed < _historySize) { _historyUsed++; } #if TRACE item.Id = _currentHistoryID.ToString(CultureInfo.InvariantCulture); #endif return id; } public SessionViewStateHistoryItem Find(Pair id) { // First make sure that the page is from the current session. DateTime uniqueID = (DateTime) id.First; if (DateTime.Compare(uniqueID, _sessionUniqueID) != 0) { return null; } // Now check if we actually still have it. int historyID = (int) id.Second; int distance = _currentHistoryID - historyID; if (distance <= 0) { // Shouldn't happen, but this would be a forward jump. return null; } else if (distance > _historyUsed) { // Gone way back. Empty history, but return null. _historyUsed = 0; return null; } else { int foundIndex = (_currentHistoryIndex + _historySize - distance) % _historySize; // Make the found item the top of the stack. _currentHistoryIndex = (foundIndex + 1) % _historySize; _currentHistoryID = historyID + 1; _historyUsed -= distance - 1; return _history[foundIndex]; } } #if TRACE public void Dump(out ArrayList arr) { arr = new ArrayList(); int n = _currentHistoryIndex; for (int i = 0; i < _historyUsed; i++) { n = n - 1; if (n == -1) { n = _history.Length - 1; } SessionViewStateHistoryItem item = _history[n]; if (item != null) { arr.Add(String.Format(CultureInfo.InvariantCulture, "{0}({1})", item.Url, item.Id)); } else { arr.Add("(null)"); } } } #endif } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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