STOCKER LE VIEWSTATE SUR LE SERVEUR PLUTÔT QUE LE CLIENT

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections.Generic;

/// <summary> 
/// This class save the viewstate value of each request on the WebServer. 
/// Don't use this on a server production ! If the application restart all the viewstates 
/// information will be loosed. You should save the viewstate in a DataBase or in any persistent storage. 
/// </summary> 
public class ServerViewStatePage : Page
{
    private static Object _lock = new object(); 
    private static Dictionary<Guid, Object> __viewstates;
    /// <summary> 
    /// Gets a dictionnary of viewstates stocked in the server. 
    /// </summary> 
    /// <value>The dictionary of viewstate stocked in the server.</value> 
    private static Dictionary<Guid, Object> _viewstates
    {
        get
        {
            lock (_lock)
            {
                if (__viewstates == null)
                    __viewstates = new Dictionary<Guid, Object>();
            }
            return __viewstates;
        }
    }

    /// <summary> 
    /// Loads any saved view-state information to the <see cref="T:System.Web.UI.Page"></see> object. 
    /// </summary> 
    /// <returns>The saved view state.</returns> 
    /// <remarks>Try to get the original viewstate if the __VIEWSTATEID hidden field was posted</remarks> 
    protected override object LoadPageStateFromPersistenceMedium()
    {
        if (!String.IsNullOrEmpty(Request.Form["__VIEWSTATEID"]))
        {
            Guid viewstateID = Guid.Empty;
            try
            {
                viewstateID = new Guid(Request.Form["__VIEWSTATEID"]);
            }
            catch
            {
                return null;
            }
            Object viewstate;
            if (_viewstates.TryGetValue(viewstateID, out viewstate))
                _viewstates.Remove(viewstateID); // Be carefull we remove the Viewstate so the user won't be able to make again the same request

            return viewstate;
        }
        else
        {
            return null;
        }
    }

    /// <summary> 
    /// Saves any view-state and control-state information for the page into a server Object. 
    /// </summary> 
    /// <param name="state">An <see cref="T:System.Object"></see> in which to store the view-state information.</param> 
    protected override void SavePageStateToPersistenceMedium(object state)
    {
        Guid viewstateID = Guid.NewGuid();
        _viewstates.Add(viewstateID, state);
        this.ClientScript.RegisterHiddenField("__VIEWSTATEID", viewstateID.ToString("N"));
    }

}