ViewState实现和优化2--自定义压缩方法采用GZipStream压缩

在序列化对象信息前先压缩数据。其实现机制也是重写基类Page 的PageStatePersister 属性

 

public class CompressPageStatePersister : PageStatePersister
{
private string PageStateKey = "____VIEWSTATE";
public CompressPageStatePersister(Page page) : base(page)
{}
public override void Load()
{
string postbackState = Page.Request.Form[PageStateKey];
if (!string.IsNullOrEmpty(postbackState))
{
//页面状态包括视图状态和控件状态两部分
Pair statePair = (Pair)CompressHelp.Decompress(postbackState);
if (!Page.EnableViewState)
{
this.ViewState = null;
}
else
{
this.ViewState = statePair.First;
}
this.ControlState = statePair.Second;
}
}
public override void Save()
{
if (!Page.EnableViewState)
{
this.ViewState = null;
}i
f (this.ViewState != null || this.ControlState != null)
{
string stateString;
Pair statePair = new Pair(ViewState, ControlState);
stateString = CompressHelp.Compress(statePair);
Page.ClientScript.RegisterHiddenField(PageStateKey, stateString);
}
}
}

//CompressHelp

public class CompressHelp
{
//序列化工具， LosFormatter 是页面默认的序列器
private static LosFormatter _formatter = new LosFormatter();
/// <summary>
/// 解压并反序列化状态内容
/// </summary>
/// <param name="stateString">从客户端取回的页面状态字符串</param>
/// <returns>还原后的页面状态Pair 对象</returns>
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];
while (true)
{
int read = zipStream.Read(buffer, 0, buffer.Length);
if (read <= 0)
{
break;
}m
sReader.Write(buffer, 0, read);
} zipStream.Close();
ms.Close();
msReader.Position = 0;
buffer = msReader.ToArray();
stateString = Convert.ToBase64String(buffer);
return _formatter.Deserialize(stateString);
}/
// <summary>
/// 序列化并压缩状态内容
/// </summary>
/// <param name="state">页面状态</param>
/// <returns>结果字符串</returns>
public static string Compress(object state)
{
StringWriter writer = new StringWriter();
_formatter.Serialize(writer, state);
string stateString = writer.ToString();
writer.Close();
byte[] buffer = Convert.FromBase64String(stateString);
MemoryStream ms = new MemoryStream();
GZipStream zipStream=new GZipStream(ms,CompressionMode.Compress,true);
zipStream.Write(buffer, 0, buffer.Length);
zipStream.Close();
buffer = new byte[ms.Length];
ms.Position = 0;
ms.Read(buffer, 0, buffer.Length);
ms.Close();
stateString = Convert.ToBase64String(buffer);
return stateString;
}
}

 //

protected override PageStatePersister PageStatePersister
{
get
{
return new CompressPageStatePersister(this);
}
}