让ViewState 保存于服务器端文件 (asp.net C#)

将ViewState持久化保持在服务器端文件的代码，这样ViewState不占用网络带宽，因此其存取只是服务器的磁盘读取时间。并且它很小，可以说是磁盘随便转一圈就能同时读取好多ViewState，因此可以说“不占时间”。为了再“不占磁盘时间”，我还使用了缓存。
创建一个基类:
public class
BasePage : System.Web.UI.Page
{
protected override object
LoadPageStatefromPersistenceMedium()
{
var viewStateID = (string)((Pair)base.LoadPageStatefromPersistenceMedium()).Second;
var stateStr = (string)Cache[viewStateID];
if (stateStr == null)
{
var fn = Path.Combine(this.Request.PhysicalApplicationPath, @"App_Data/ViewState/" + viewStateID);
stateStr = File.ReadAllText(fn);
}
return new ObjectStateFormatter().Deserialize(stateStr);
}
protected override void
SavePageStateToPersistenceMedium(object state)
{
var value = new ObjectStateFormatter().Serialize(state);
var viewStateID = (DateTime.Now.Ticks + (long)this.GetHashCode()).ToString(); //产生离散的id号码
var fn = Path.Combine(this.Request.PhysicalApplicationPath, @"App_Data/ViewState/" + viewStateID);
ThreadPool.QueueUserWorkItem(obj => File.WriteAllText(fn, value));
Cache.Insert(viewStateID, value);
base.SavePageStateToPersistenceMedium(viewStateID);
}

}
}
Global.asax,以下代码也可以不用：
protected void
Application_Start(object sender, EventArgs e)
{
DirectoryInfo dir = new DirectoryInfo(this.Server.MapPath("~/App_Data/ViewState/"));
if (!dir.Exists)
dir.Create();
else
{
DateTime nt = DateTime.Now.AddHours(-0.3); //删除15分钟以前的缓存文件
FileInfo[] fiArr = dir.GetFiles();
foreach (FileInfo f in fiArr)
{
if (f.CreationTime < nt)
{
f.Delete();
}
}
}
}
使用方法:
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