ViewState持久化方法

网上找来的代码，备用。具体如下：

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);
            if (File.Exists(fn)) //防止删除报错
            {
                stateStr = File.ReadAllText(fn);
            }
        }
        return new ObjectStateFormatter().Deserialize(stateStr);
    }

    protected override void SavePageStateToPersistenceMedium(object state)
    {
        var value = new ObjectStateFormatter().Serialize(state);  //获取页面状态
        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)); //插入线程池中，写入硬盘
        Cache.Insert(viewStateID, value);   //用sesson也可以
        base.SavePageStateToPersistenceMedium(viewStateID);

    }

这样viewstate已经存入硬盘，持久化目标达成。但为了防止临时文件越来越大，添加一个定期清理的方法在Global.asax的Application_Start中添加如下方法

    if (!dir.Exists)
            dir.Create();
        else
        {
            var nt = DateTime.Now.AddHours(-1); //1小时过期
            foreach (var item in dir.GetFiles())
            {
                if (item.CreationTime < nt)
                    item.Delete();
            }
        }