关于控件postback 后viewstate加载失败的问题

我写了一个控件Inherits TextBox，里面有一个复杂属性Tip，但每次postback的时候都说加载viewstate失败，除非我在!postback的情况下给Tip.xxx赋值.

下面我贴出代码，我已经搞了一天了，搞不出什么原因。

JTextBox控件

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Madou.WebControls
{
    [DefaultProperty("Text")]
    [ParseChildren(true), PersistChildren(false)]
    [ToolboxData("<{0}:JTextBox runat=server></{0}:JTextBox>")]
    public class JTextBox : System.Web.UI.WebControls.TextBox
    {

        public JTextBox()
        {
            BackColor = System.Drawing.Color.Beige;
           
        }

        "Private"#region"Private"
        private ClipTipComponent _tip;
        #endregion

        "定义属性"#region"定义属性"
        [Bindable(true)]
        [Category("Behavior")]
        [Description("Tip")]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]        
        [PersistenceMode(PersistenceMode.InnerProperty)]
        [NotifyParentProperty(true)]
        public virtual ClipTipComponent Tip
        {
            get
            {
                if (_tip == null)
                {
                    _tip = new ClipTipComponent();
                    if (IsTrackingViewState)
                    {
                        ((IStateManager)_tip).TrackViewState();
                    }

                }
                return _tip;
            }
        }

        #endregion

        "override"#region"override"

     
        state management#region state management
        protected override void LoadViewState(object savedState)
        {
            Pair p = savedState as Pair;
            //HttpContext.Current.Response.Write(savedState.GetType().ToString());
           // HttpContext.Current.Response.Write(savedState==null);
           // HttpContext.Current.Response.End();
            if (p != null)
            {
                base.LoadViewState(p.First);
                ((IStateManager)Tip).LoadViewState(p.Second);
               
            }
            else
            {
                base.LoadViewState(savedState);
            }
          
        }

        protected override object SaveViewState()
        {
            object baseState = base.SaveViewState();
            object thisState = null;

            if (Tip != null)
            {
                thisState = ((IStateManager)Tip).SaveViewState();
            }

            if (thisState != null)
            {
                return new Pair(baseState, thisState);
            }
            else
            {
                return baseState;
            }

        }

        protected override void TrackViewState()
        {
            if (_tip != null)
            {
                ((IStateManager)_tip).TrackViewState();
            }
            base.TrackViewState();
        }
        #endregion

        protected override void OnPreRender(EventArgs e)
        {
            Tip.RegisterJs(this);
            base.OnPreRender(e);
        }
        protected override void OnLoad(EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                Tip.CloseText = "关闭";
            }
            base.OnLoad(e);
        }

        #endregion
    }
}

Tip属性类

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Madou.WebControls.Converter;
namespace Madou.WebControls
{
    [TypeConverter(typeof(ClipTipComponentConverter))]
    public class ClipTipComponent : IStateManager
    {
        "Private"#region"Private"
        private bool _isTrackingViewState;
        private StateBag _viewState;
        #endregion

        public ClipTipComponent() { }

        "属性"#region"属性"
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("是否启用Ajax效果")]
        [NotifyParentProperty(true)]
        public bool EnabledAjax
        {
            get
            {
                return ViewState["EnabledAjax"] == null ? false : Convert.ToBoolean(ViewState["EnabledAjax"]);
            }
            set
            {
                ViewState["EnabledAjax"] = value;
            }
        }

      

        /**//// <summary>
        /// 是否使用Tip功能
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(true)]
        [Description("是否使用ClipTip功能")]
        [NotifyParentProperty(true)]
        public bool EnabledClipTip
        {
            get
            {
                return ViewState["EnabledClipTip"] == null ? true : Convert.ToBoolean(ViewState["EnabledClipTip"]);
            }
            set
            {
                ViewState["EnabledClipTip"] = value;
            }
        }
        /**//// <summary>
        /// // The width of the clueTip
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("275")]
        [Description("The width of the clueTip")]
        [NotifyParentProperty(true)]
        public string TipWidth
        {
            get
            {
                return ViewState["TipWidth"] == null ? "275" : ViewState["TipWidth"].ToString();
            }
            set
            {
                ViewState["TipWidth"] = value;

            }
        }
        /**//// <summary>
        /// // The height of the clueTip.
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("auto")]
        [Description("The height of the clueTip")]
        [NotifyParentProperty(true)]
        public string TipHeigth
        {
            get
            {
                return ViewState["TipHeigth"] == null ? "auto" : ViewState["TipHeigth"].ToString();
            }
            set
            {
                ViewState["TipHeigth"] = value;
            }
        }

        /**//// <summary>
        /// A character used to split the title attribute into the clueTip title and divs
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("")]
        [Description("A character used to split the title attribute into the clueTip title and divs")]
        [NotifyParentProperty(true)]
        public string SplitTitle
        {
            get
            {
                return ViewState["SplitTitle"] == null ? string.Empty : Convert.ToString(ViewState["SplitTitle"]);
            }
            set
            {
                ViewState["SplitTitle"] = value;
            }
        }

        /**//// <summary>
        /// show title bar of the clueTip, even if title attribute not set
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(true)]
        [Description("show title bar of the clueTip, even if title attribute not set")]
        [NotifyParentProperty(true)]
        public bool ShowTitle
        {
            get
            {
                return ViewState["ShowTitle"] == null ? true : Convert.ToBoolean(ViewState["ShowTitle"]);
            }
            set
            {
                ViewState["ShowTitle"] = value;
            }
        }
        /**//// <summary>
        /// his is also used for a "directional" class on the same div, depending on where the clueTip is in relation to the invoking element. The class appears in the form of 'cluetip-' + direction + cluetipClass. this allows you to create your own clueTip theme in a separate CSS file or use one of the three pre-packaged themes: default, jtip, or rounded.
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("default")]
        [Description("default, jtip, or rounded")]
        [NotifyParentProperty(true)]
        [Bindable(false)]
        [TypeConverter(typeof(Madou.WebControls.Converter.ClueTipClassConverter))]
        public string ClueTipClass
        {
            get
            {
                return ViewState["ClueTipClass"] == null ? "default" : Convert.ToString(ViewState["ClueTipClass"]);
            }
            set
            {
                ViewState["ClueTipClass"] = value;
            }
        }

        /**//// <summary>
        /// class applied to the invoking element onmouseover and removed onmouseout
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("")]
        [Description("class applied to the invoking element onmouseover and removed onmouseout")]
        [NotifyParentProperty(true)]
        public string HoverClass
        {
            get
            {
                return ViewState["HoverClass"] == null ? string.Empty : Convert.ToString(ViewState["HoverClass"]);
            }
            set
            {
                ViewState["HoverClass"] = value;
            }
        }



        /**//// <summary>
        /// if true, displays arrow on appropriate side of clueTip. more info below [8]
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("if true, displays arrow on appropriate side of clueTip")]
        [NotifyParentProperty(true)]
        public bool Arrows
        {
            get
            {
                return ViewState["Arrows"] == null ? false : Convert.ToBoolean(ViewState["Arrows"]);
            }
            set
            {
                ViewState["Arrows"] = value;
            }
        }

        [Category("Behavior")]
        [DefaultValue(true)]
        [Description("是否有Shadow")]
        [NotifyParentProperty(true)]
        public bool DropShadow
        {
            get
            {
                return ViewState["DropShadow"] == null ? true : Convert.ToBoolean(ViewState["DropShadow"]);
            }
            set
            {
                ViewState["DropShadow"] = value;
            }
        }

        [Category("Behavior")]
        [DefaultValue(6)]
        [Description("Shadow Steps")]
        [NotifyParentProperty(true)]
        public int DropShadowSteps
        {
            get
            {
                return ViewState["DropShadowSteps"] == null ? 6 : Convert.ToInt32(ViewState["DropShadowSteps"]);
            }
            set
            {
                ViewState["DropShadowSteps"] = value;
            }
        }

        /**//// <summary>
        /// 如果ture,鼠标点击close才关闭
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("如果ture,鼠标点击close才关闭")]
        [NotifyParentProperty(true)]
        public bool Sticky
        {
            get
            {
                return ViewState["Sticky"] == null ? false : Convert.ToBoolean(ViewState["Sticky"]);
            }
            set
            {
                ViewState["Sticky"] = value;
            }
        }

        /**//// <summary>
        /// close when clueTip is moused out
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("close when clueTip is moused out")]
        [NotifyParentProperty(true)]
        public bool MouseOutClose
        {
            get
            {
                return ViewState["MouseOutClose"] == null ? false : Convert.ToBoolean(ViewState["MouseOutClose"]);
            }
            set
            {
                ViewState["MouseOutClose"] = value;
            }
        }

        /**//// <summary>
        ///   'hover'OR 'click',  // set to 'click' to force user to click to show clueTip
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("hover")]
        [Description("hover'OR 'click'")]
        [NotifyParentProperty(true)]
        [TypeConverter(typeof(Madou.WebControls.Converter.ActivationConverter))]
        public string Activation
        {
            get
            {
                return ViewState["Activation"] == null ? "hover" : ViewState["Activation"].ToString();
            }
            set
            {
                ViewState["Activation"] = value;
            }
        }

        /**//// <summary>
        /// if true, and activation is not 'click', then clicking on a clueTipped link will take user to 
        /// the link's href, even if href and tipAttribute are equal
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("if true, and activation is not 'click'")]
        [NotifyParentProperty(true)]
        public bool ClickThrough
        {
            get
            {
                return ViewState["ClickThrough"] == null ? false : Convert.ToBoolean(ViewState["ClickThrough"]);
            }
            set
            {
                ViewState["ClickThrough"] = value;
            }
        }

        /**//// <summary>
        ///  // if true, clueTip will track mouse movement (experimental)
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(false)]
        [Description("if true, clueTip will track mouse movement (experimental)")]
        [NotifyParentProperty(true)]
        public bool Tracking
        {
            get
            {
                return ViewState["Tracking"] == null ? false : Convert.ToBoolean(ViewState["Tracking"]);
            }
            set
            {
                ViewState["Tracking"] = value;
            }
        }

        /**//// <summary>
        ///  close clueTip on a timed delay (experimental)
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(0)]
        [Description("close clueTip on a timed delay (experimental)")]
        [NotifyParentProperty(true)]
        public int DelaydClose
        {
            get
            {
                return ViewState["DelaydClose"] == null ? 0 : Convert.ToInt32(ViewState["DelaydClose"]);
            }
            set
            {
                ViewState["DelaydClose"] = value;
            }
        }

        /**//// <summary>
        /// location of close text for sticky cluetips; can be 'top' or 'bottom' or 'title'
        /// </summary>
        [Category("Behavior")]
        [DefaultValue("top")]
        [Description("location of close text for sticky cluetips; can be 'top' or 'bottom' or 'title'")]
        [NotifyParentProperty(true)]
        [TypeConverter(typeof(Madou.WebControls.Converter.ClosePositionConverter))]
        public string ClosePosition
        {
            get
            {
                return ViewState["ClosePosition"] == null ? "top" : ViewState["ClosePosition"].ToString();
            }
            set
            {
                ViewState["ClosePosition"] = value;
            }
        }

        [Category("Behavior")]
        [DefaultValue("关闭")]
        [Description("Close Text")]
        [NotifyParentProperty(true)]
        public string CloseText
        {
            get
            {
                return ViewState["CloseText"] == null ? "关闭" : ViewState["CloseText"].ToString();
            }
            set
            {
                ViewState["CloseText"] = value;
            }
        }
        /**//// <summary>
        /// 字符数
        /// </summary>
        [Category("Behavior")]
        [DefaultValue(0)]
        [Description("字符数")]
        [NotifyParentProperty(true)]
        public int Truncate
        {
            get
            {
                return ViewState["Truncate"] == null ? 0 : Convert.ToInt32(ViewState["Truncate"]);
            }
            set
            {
                ViewState["Truncate"] = value;
            }
        }

        #endregion

        "HELP#region"HELP

        protected virtual StateBag ViewState
        {
            get
            {
                if (_viewState == null)
                {
                    _viewState = new StateBag(true);
                    if (_isTrackingViewState)
                        ((IStateManager)_viewState).TrackViewState();

                }
                return _viewState;
            }
        }              

        #endregion

        "重写的方法"#region"重写的方法"
        public override string ToString()
        {
            return ToString(System.Globalization.CultureInfo.InvariantCulture);
        }
        public string ToString(System.Globalization.CultureInfo culture)
        {
            return TypeDescriptor.GetConverter(GetType()).ConvertToString(null, culture, this);
        }


        #endregion

        IStateManager Members#region IStateManager Members

        bool IStateManager.IsTrackingViewState
        {
            get { return _isTrackingViewState; }
        }

        void IStateManager.LoadViewState(object state)
        {
          
            if (state != null)
            {
                ((IStateManager)ViewState).LoadViewState(state);

            }           
           
        }

        object IStateManager.SaveViewState()
        {
            object savedState = null;
            if (_viewState != null)
            {
                savedState = ((IStateManager)_viewState).SaveViewState();                     
            }
            else{
            // HttpContext.Current.Response.Write("saveState1=false");  
            }
            return savedState;
        }

        void IStateManager.TrackViewState()
        {
            _isTrackingViewState = true;
            if (_viewState != null)
            {
                ((IStateManager)_viewState).TrackViewState();
            }
        }

        #endregion

        

        internal void SetDirty()
        {
            _viewState.SetDirty(true);
        }

       internal void RegisterJs(Control target, string clientId)
        {
            if (target is WebControl)
            {
                string tooltip = (target as WebControl).ToolTip;
                if (string.IsNullOrEmpty(tooltip.Trim()))
                {
                    if (!EnabledAjax)
                        return;
                }

            }
           
            if (EnabledClipTip)
            {
                JavaScriptWriter w = new JavaScriptWriter();
                w.AddLine("$(function()");

                w.OpenBlock();
                if (!EnabledAjax)
                {
                    if (string.IsNullOrEmpty(SplitTitle))
                        SplitTitle = "|";
                    w.AddLine("$('#" + clientId + "').cluetip({splitTitle: '" + SplitTitle + "'");
                }
                else
                {
                    w.AddLine("$('#" + clientId + "').cluetip({splitTitle: ''");
                }
                w.AddJSONItem("cluetipClass", ClueTipClass);
                w.AddJSONItem("hoverClass", HoverClass);
                w.AddJSONItem("arrows", Arrows);
                w.AddJSONItem("dropShadow", DropShadow);
                w.AddJSONItem("dropShadowSteps", DropShadowSteps);
                w.AddJSONItem("sticky", Sticky);
                w.AddJSONItem("mouseOutClose", MouseOutClose);
                w.AddJSONItem("activation", Activation);
                w.AddJSONItem("clickThrough", ClickThrough);
                w.AddJSONItem("tracking", Tracking);
                w.AddJSONItem("delayedClose", DelaydClose);
                w.AddJSONItem("closePosition", ClosePosition);
                w.AddJSONItem("width", TipWidth);
                w.AddJSONItem("height", TipHeigth);
                w.AddJSONItem("closeText", CloseText);
                w.AddJSONItem("truncate", Truncate);

                w.AddLine("});");
                w.CloseBlock();
                w.AddLine(");");

                target.Page.ClientScript.RegisterClientScriptBlock(target.GetType(), clientId, w.ToString(), false);
            }
        }

      internal void RegisterJs(Control target)
        {
            string clientId = target.ClientID;
            RegisterJs(target, clientId);
        }
    }
}

出现的问题，一定要在!PostBack给Tip.xxx赋值，否则出现viewstate不能正常加载的错误提示(如果给JTextBox的Text赋值的话),请问这个是什么原因 ！
bug已经发现，原来System.Web.UI.WebControls.TextBox的SaveViewState()已经是Pair