basechildnode.cs

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//------------------------------------------------------------------------------
// Copyright (c) 2000-2003 Microsoft Corporation. All Rights Reserved.
//------------------------------------------------------------------------------

namespace Microsoft.Web.UI.WebControls
{
    using System;
    using System.Web.UI;
    using System.Reflection;
    using System.ComponentModel;

    /// <summary>
    /// Base class for child nodes of parent controls.
    /// </summary>
    [DefaultProperty("ID")]
    public abstract class BaseChildNode : ICloneable, IStateManager
    {
        private bool _IsTrackingViewState = false;
        private StateBag _ViewState;
        
        /// <summary>
        /// Returns a String that represents the current Object.
        /// </summary>
        /// <returns>A String that represents the current Object.</returns>
        public override string ToString()
        {
            if (ID != String.Empty)
            {
                return ID;
            }
            else
            {
                return this.GetType().Name;
            }
        }

        /// <summary>
        /// Returns the parent object.
        /// </summary>
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        [Browsable(false)]
        public abstract object Parent
        { 
            get;
        }

        /// <summary>
        /// Adds attributes to the HtmlTextWriter.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the content.</param>
        protected virtual void AddAttributesToRender(HtmlTextWriter writer)
        {
            if (ID != String.Empty)
            {
                writer.AddAttribute("ID", ID);
            }
        }

        /// <summary>
        /// Writes attributes to the HtmlTextWriter.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the content.</param>
        protected virtual void WriteAttributes(HtmlTextWriter writer)
        {
            if (ID != String.Empty)
            {
                writer.WriteAttribute("ID", ID);
            }
        }

        /// <summary>
        /// Implement the UpLevel rendering path in this method.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the content.</param>
        protected abstract void RenderUpLevelPath(HtmlTextWriter writer);

        /// <summary>
        /// Implement the DownLevel rendering path in this method.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the content.</param>
        protected abstract void RenderDownLevelPath(HtmlTextWriter writer);

        /// <summary>
        /// Implement the Designer rendering path in this method.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the content.</param>
        protected abstract void RenderDesignerPath(HtmlTextWriter writer);

        /// <summary>
        /// Outputs content to a provided HtmlTextWriter output stream.
        /// </summary>
        /// <param name="writer">The HtmlTextWriter object that receives the control content.</param>
        /// <param name="pathID">The ID (from BaseRichControl) of the rendering path to use.</param>
        protected internal virtual void Render(HtmlTextWriter writer, RenderPathID pathID)
        {
            switch (pathID)
            {
                case RenderPathID.DownLevelPath:
                    RenderDownLevelPath(writer);
                    break;

                case RenderPathID.UpLevelPath:
                    RenderUpLevelPath(writer);
                    break;

                case RenderPathID.DesignerPath:
                    RenderDesignerPath(writer);
                    break;
            }
        }

        /// <summary>
        /// The ID of the node.
        /// </summary>
        [DefaultValue("")]
        [ParenthesizePropertyName(true)]
        [ResDescription("BaseID")]
        public virtual string ID
        {
            get
            {
                object obj = ViewState["ID"];
                return (obj == null) ? String.Empty : (string)obj;
            }

            set { ViewState["ID"] = value; }
        }

        /// <summary>
        /// Sets all items within the StateBag to be dirty
        /// </summary>
        protected internal virtual void SetViewStateDirty()
        {
            if (_ViewState != null)
            {
                foreach (StateItem item in ViewState.Values)
                {
                    item.IsDirty = true;
                }
            }
        }

        /// <summary>
        /// Sets all items within the StateBag to be clean
        /// </summary>
        protected internal virtual void SetViewStateClean()
        {
            if (_ViewState != null)
            {
                foreach (StateItem item in ViewState.Values)
                {
                    item.IsDirty = false;
                }
            }
        }

        /// <summary>
        /// Creates a new object that is a copy of the current instance.
        /// </summary>
        /// <returns>A new object that is a copy of this instance.</returns>
        public virtual object Clone()
        {
            BaseChildNode copy = (BaseChildNode)Activator.CreateInstance(this.GetType(), BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.CreateInstance, null, null, null);

            // Merge in the properties from this object into the copy
            copy._IsTrackingViewState = this._IsTrackingViewState;

            if (this._ViewState != null)
            {
                StateBag viewState = copy.ViewState;
                foreach (string key in this.ViewState.Keys)
                {
                    object item = this.ViewState[key];
                    if (item is ICloneable)
                    {
                        item = ((ICloneable)item).Clone();
                    }

                    viewState[key] = item;
                }
            }

            return copy;
        }

        /// <summary>
        /// An instance of the StateBag class that contains the view state information.
        /// </summary>
        protected StateBag ViewState
        {
            get
            {
                // To concerve resources, especially on the page,
                // only create the view state when needed.
                if (_ViewState == null)
                {
                    _ViewState = new StateBag();
                    if (((IStateManager)this).IsTrackingViewState)
                    {
                        ((IStateManager)_ViewState).TrackViewState();
                    }
                }

                return _ViewState;
            }
        }

        /// <summary>
        /// Loads the node's previously saved view state.
        /// </summary>
        /// <param name="state">An Object that contains the saved view state values for the node.</param>
        void IStateManager.LoadViewState(object state)
        {
            ((BaseChildNode)this).LoadViewState(state);
        }

        /// <summary>
        /// Loads the node's previously saved view state.
        /// </summary>
        /// <param name="state">An Object that contains the saved view state values for the node.</param>
        protected virtual void LoadViewState(object state)
        {
            if (state != null)
            {
                ((IStateManager)ViewState).LoadViewState(state);
            }
        }

        /// <summary>
        /// Saves the changes to the node's view state to an Object.
        /// </summary>
        /// <returns>The Object that contains the view state changes.</returns>
        object IStateManager.SaveViewState()
        {
            return ((BaseChildNode)this).SaveViewState();
        }

        /// <summary>
        /// Saves the changes to the node's view state to an Object.
        /// </summary>
        /// <returns>The Object that contains the view state changes.</returns>
        protected virtual object SaveViewState()
        {
            if (_ViewState != null)
            {
                return ((IStateManager)_ViewState).SaveViewState();
            }

            return null;
        }

        /// <summary>
        /// Instructs the node to track changes to its view state.
        /// </summary>
        void IStateManager.TrackViewState()
        {
            ((BaseChildNode)this).TrackViewState();
        }

        /// <summary>
        /// Instructs the node to track changes to its view state.
        /// </summary>
        protected virtual void TrackViewState()
        {
            _IsTrackingViewState = true;

            if (_ViewState != null)
            {
                ((IStateManager)_ViewState).TrackViewState();
            }
        }

        /// <summary>
        /// Gets a value indicating whether a server control is tracking its view state changes.
        /// </summary>
        bool IStateManager.IsTrackingViewState
        {
            get { return _IsTrackingViewState; }
        }
    }
}