四:理解Page类的运行机制(例:基于PageStatePersister的页面状态存取)

using System;
using System.IO;
using System.IO.Compression;
using System.Web.UI;
/// <summary>
///GZipCompress 的摘要说明
/// </summary>
public class GZipCompress
{
    //LosFormatter序列化web窗体页的视图状态
    private static LosFormatter _formater = new LosFormatter();
    public GZipCompress()
    {}
    //带压缩功能的序列化
    public static string Compress(object state)
    {
        StringWriter writer = new StringWriter();
        //序列化状态
        _formater.Serialize(writer, state);
        //取得序列化结果
        string stateString = writer.ToString();
        writer.Close();
        //将字符串转换成八位无符号整数数组
        byte[] buffer = Convert.FromBase64String(stateString);
        MemoryStream ms = new MemoryStream();
        //搞一个压缩流出来，将流保持为打开的状态
        GZipStream zipStream = new GZipStream(ms, CompressionMode.Compress, true);
        zipStream.Write(buffer, 0, buffer.Length);
        zipStream.Close();
        buffer = new byte[ms.Length];
        //获取或设置流中的当前位置
        ms.Position = 0;
        ms.Read(buffer, 0, buffer.Length);
        ms.Close();
        //将压缩结果转成字符串，便于保存在页面中
        stateString = Convert.ToBase64String(buffer);
        return stateString;
    }
    public static object Decompress(string stateString)
    {
        byte[] buffer = Convert.FromBase64String(stateString);
        MemoryStream ms = new MemoryStream(buffer);
        GZipStream zipStream = new GZipStream(ms, CompressionMode.Decompress);
        MemoryStream msReader = new MemoryStream();
        buffer = new byte[0x1000];//开辟0x1000个字节空间16*16*16=4K
        while (true)
        {
            int read = zipStream.Read(buffer, 0, buffer.Length);
            if (read <= 0)
            { break; }
            msReader.Write(buffer, 0, read);
        }
        zipStream.Close();
        ms.Close();
        msReader.Position = 0;
        buffer = msReader.ToArray();
        stateString = Convert.ToBase64String(buffer);
        return _formater.Deserialize(stateString);
    }
}

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.IO;
using System.IO.Compression;
/// <summary>
///PageStatePersister 的摘要说明
/// </summary>
public class CompressPageStatePersister:PageStatePersister
{
    private const string STATEKEY = "____VIEWSTATE";
    //调用基类构造函数
    public CompressPageStatePersister(Page page) : base(page) { }
    
    //加载页面状态
    public override void Load()
    {
        //取得保存在客户端的状态内容
        string postbackstate = Page.Request.Form[STATEKEY];
        if (!string.IsNullOrEmpty(postbackstate))
        {
            //解压，反序列化
            //asp.net的viewstate包括控件状态和视图状态
            //存储两个相关对象
            Pair statePair = (Pair)GZipCompress.Decompress(postbackstate);
            if (Page.EnableViewState)
            {
                ViewState = null;
            }
            else
            {
                ViewState = statePair.First;
            }
            ControlState = statePair.Second;
        }       
    }
    //保存页面状态
    public override void Save()
    {
        if (!Page.EnableViewState)
        {
            ViewState = null;
        }
        if (ViewState != null || ControlState != null)
        {
            string stateString;
            Pair statePair = new Pair(ViewState, ControlState);
            //序列化，压缩
            stateString = GZipCompress.Compress(statePair);
            //把页面状态注册到页面上
            Page.ClientScript.RegisterHiddenField(STATEKEY, stateString);
        }
    }
}

<?xml version="1.0"?>
<configuration>
  <appSettings/>
  <connectionStrings>
    <add name="AntMallConnectionString" connectionString="Data Source=192.168.1.186;Initial Catalog=AntMall;Integrated Security=True"
      providerName="System.Data.SqlClient" />
  </connectionStrings>
  <system.web>
    <compilation debug="true"></compilation>
    <authentication mode="Forms"/>
  </system.web>
</configuration>

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>    
        <asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
            DataSourceID="SqlDataSource1" AutoGenerateColumns="False">
            <Columns>
                <asp:BoundField DataField="title" HeaderText="title" SortExpression="title" />
                <asp:BoundField DataField="memo" HeaderText="memo" SortExpression="memo" />
                <asp:BoundField DataField="fullPrice" HeaderText="fullPrice" 
                    SortExpression="fullPrice" />
                <asp:BoundField DataField="defaultPic" HeaderText="defaultPic" 
                    SortExpression="defaultPic" />
                <asp:BoundField DataField="inputTime" HeaderText="inputTime" 
                    SortExpression="inputTime" />
            </Columns>
        </asp:GridView>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
            ConnectionString="<%$ ConnectionStrings:AntMallConnectionString %>" 
            SelectCommand="SELECT [fullPrice], [inputTime], [memo], [title], [defaultPic] FROM [Product]">
        </asp:SqlDataSource>    
    </div>
    </form>
</body>
</html>

using System;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
public partial class _Default : System.Web.UI.Page
{
    #region 重写PageStatePersister定制页面状态持久化行为
    CompressPageStatePersister _pageStatePersister = null;
    protected override PageStatePersister PageStatePersister
    {
        get
        {
            if (_pageStatePersister == null)
            {
                _pageStatePersister = new CompressPageStatePersister(this);
            }
            return _pageStatePersister;
        }
    }
    #endregion
    protected void Page_Load(object sender, EventArgs e)
    {
    }
}