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。

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
    }
}

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["