ViewState保存在服务器，可定时清空

通过csdn中sp1234的帖子进行整理

ViewstateMethod.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;
using System.Web.UI;
using System.Threading;


/// <summary>
///ViewstateMethod 的摘要说明
/// </summary>

namespace Lear
{
    public class ViewstateMethod : System.Web.UI.Page
    {
            #region 解决ViewState过于庞大的问题
            protected override object LoadPageStateFromPersistenceMedium()
            {
                string viewStateID = (string)((Pair)base.LoadPageStateFromPersistenceMedium()).Second;
                string stateObject = (string)Cache[viewStateID];
                if (stateObject != null)
                {
                    Cache.Remove(viewStateID);
                    return stateObject;
                }

                string fn = Path.Combine(this.Request.PhysicalApplicationPath, @"App_Data/ViewState/" + viewStateID);
                string stateStr = File.ReadAllText(fn);
                return new ObjectStateFormatter().Deserialize(stateStr);
            }

            protected override void SavePageStateToPersistenceMedium(object state)
            {
                string viewStateID = (DateTime.Now.Ticks + (long)this.GetHashCode()).ToString(); //产生离散的id号码
                Cache.Insert(viewStateID, state);
                //ThreadPool.QueueUserWorkItem(obj =>
                //{
                    string value = new ObjectStateFormatter().Serialize(state);
                    string fn = Path.Combine(this.Request.PhysicalApplicationPath, @"App_Data/ViewState/" + viewStateID);
                    File.WriteAllText(fn, value);
                //});
                base.SavePageStateToPersistenceMedium(viewStateID);
            }
            #endregion
    }
}

定时删除Viewstate文件方法，在Page_Load中调用，时间自行调整，建议放在root.master.cs文件中（最外层的模版）

    #region 删除ViewState中过时的信息
    private void DelViewstateForApplication()
    {
        if (Application["delDatetime"] != null)
        {
            DateTime thisNow = System.DateTime.Now;
            DateTime lastNow = thisNow;
            DateTime delDatetime = Convert.ToDateTime(Application["delDatetime"]);
            if ((thisNow - delDatetime).Minutes > 1)//时间自行调整
            {
                lock (Application)
                {
                    if (delDatetime == Convert.ToDateTime(Application["delDatetime"]))
                    {
                        lastNow = Convert.ToDateTime(Application["delDatetime"]);
                        Application["delDatetime"] = System.DateTime.Now;
                    }
                }
            }
            if (thisNow != lastNow)
                DelViewStateData();
        }
        else
        {
            bool first = false;
            lock (Application)
            {
                if (Application["delDatetime"] == null)
                {
                    Application["delDatetime"] = System.DateTime.Now;
                    first = true;
                }
            }
            if (first)
                DelViewStateData();
        }
    }

    private void DelViewStateData()
    {
        System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(this.Server.MapPath("~/App_Data/ViewState/"));
        if (!dir.Exists)
            dir.Create();
        else
        {
            DateTime nt = DateTime.Now.AddMinutes(-1);//时间自行调整
            foreach (System.IO.FileInfo f in dir.GetFiles())
            {
                if (f.CreationTime < nt)
                    f.Delete();
            }
        }
    }
    #endregion

最终aspx页面使用方法：如default.aspx.cs文件中的类需要继承自Lear.ViewstateMethod，而不是System.Web.UI.Page

没有交互提交的页面，可在头部Page中加入EnableViewState="false"以减小数据大小，直接继承System.Web.UI.Page，而不继承自Lear.ViewstateMethod生成多余的Viewstate文件。

正常的页面可以关掉EnableViewState="false" EnableViewStateMac="false" EnableEventValidation="false"

注：本方法只是个人总结，请慎重使用。