自定义视图状态管理

本实例实现了对复杂属性MyPerson的状态管理

1、要想实现对MyPerson的状态管理，首先此类要实现IStateManager接口,

其中void IStateManager.LoadViewState(object state)实现对上次保存的视图状态的加载。

而 object IStateManager.SaveViewState()保存本次视图状态。

此两个方法实现的是完全相反的操作，如下类中代码所示。

2、控件类可以是继承自Control,也可以是继承自WebControl

    并且要重写控件生命周期中会触发的

   protected override void LoadViewState(object savedState)

   protected override object SaveViewState()

   在这两个方法中分别来调用MyPerson类中的

   void IStateManager.LoadViewState(object state)

   object IStateManager.SaveViewState()

   否则MyPerson类中的以上两个方法，永远不会被执行。

    [DefaultProperty("Text")]
    [ToolboxData("<{0}:PersonViewState runat=server></{0}:PersonViewState>")]
    public class PersonViewState : WebControl
    {
        private MyPerson myPerson;
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        [NotifyParentProperty(true)]
        [PersistenceMode(PersistenceMode.Attribute)]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        public MyPerson MyPerson
        {
            get 
            {
                if (myPerson == null)
                    myPerson = new MyPerson();
                if (IsTrackingViewState)
                    ((IStateManager)myPerson).TrackViewState();
                return myPerson;
            }            
        }
        protected override void LoadViewState(object savedState)
        {
            Pair pair = (Pair)savedState;
            base.LoadViewState(pair.First);
            ((IStateManager)myPerson).LoadViewState(pair.Second);
           
        }
        protected override object SaveViewState()
        {
            Pair pair = new Pair();
            pair.First = base.SaveViewState();
            pair.Second = ((IStateManager)myPerson).SaveViewState();
            return pair;
        }
        protected override void RenderContents(HtmlTextWriter output)
        {
            string msg = "我的名字是："+MyPerson.MyName+" 我的年龄是："+MyPerson.MyAge;
            output.Write("应用视图保存信息："+msg);
        }
    }
    [TypeConverter(typeof(ExpandableObjectConverter))]
    public class MyPerson:IStateManager
    {
        private string myName;
        [NotifyParentProperty(true)]
        public string MyName
        {
            get { return myName; }
            set { myName = value; }
        }
        private string myAge;
        [NotifyParentProperty(true)]
        public string MyAge
        {
            get { return myAge; }
            set { myAge = value; }
        }
        #region IStateManager 成员
        private bool _IsTrackingViewState = true;
        bool IStateManager.IsTrackingViewState
        {
            get
            {
                return _IsTrackingViewState;
            }
        }
        void IStateManager.LoadViewState(object state)
        {
            if (state == null)
                return;
            object[] myState = (object[])state;
            myName = myState[0].ToString();
            myAge = myState[1].ToString();
        }
        object IStateManager.SaveViewState()
        {
            object[] state = new object[2];
            state[0] = myName;
            state[1] = myAge;
            return state;
        }
        void IStateManager.TrackViewState()
        {
            this._IsTrackingViewState = true;
        }
        #endregion
    }