Underdand one delegate usage via A tree class

 One week ago, I surfed a forum and got a tree class template. It has some a little diffrence from what I knew before. I used this class template to deal with a work task. Spending two hours，I just understood what its conception.

 

Original Class Code:

 public delegate void TreeVisitor<T>(T nodeData);

   public class NTree<T>
    {
       public T data;
        LinkedList<NTree<T>> children;

        public NTree(T data)
        {
            this.data = data;
            children = new LinkedList<NTree<T>>();
        }

        public void addChild(T data)
        {
            children.AddFirst(new NTree<T>(data));
        }

        public NTree<T> getChild(int i)
        {
            foreach (NTree<T> n in children)
                if (--i == 0) return n;
            return null;
        }

        public void traverse(NTree<T> node, TreeVisitor<T> visitor)//here is visitor pattern
        {
            visitor(node.data);
            foreach (NTree<T> kid in node.children)
                traverse(kid, visitor);
        }

       
    }

 

I Created a node data clas

public class NodeData
   {
       string _text = null;

       public string Text
       {
           get { return _text; }
           set { _text = value; }
       }

       string _url = null;

       public string Url
       {
           get { return _url; }
           set { _url = value; }
       }

       int? _id = null;

       public int? Id
       {
           get { return _id; }
           set { _id = value; }
       }


       /// <summary>
       /// 0-root
       /// 1-channel
       /// 2-column
       /// </summary>
       int? _type = null;

       public int? Type
       {
           get { return _type; }
           set { _type = value; }
       }

       int? _parentId = null;

       public int? ParentId
       {
           get { return _parentId; }
           set { _parentId = value; }
       }
       
   }

 

My points are first traverse  a tree to generate its nodes and then traverse it to create a menu for default page .

 

 public class Navigator
    {
        protected NTree<NodeData> node;//represent
        protected void CreataNavigatorTree()
        {
            TreeVisitor<NodeData> TreeVisitor = TreeCreate;

            NodeData rootData = new NodeData();
            rootData.Text = "root";
            rootData.Url = null;
            rootData.Type = 0;
            node = new NTree<NodeData>(rootData);

            node.traverse(node, TreeVisitor);//Create Tree           

        }

        void TreeCreate<T>(T TNode)
        {

            NodeData data = TNode as NodeData;
            if (data.Type == 0)
            {
                IList<KyChannel> lstChan = KyChannel.GetAll();
                foreach (KyChannel chan in lstChan)
                {
                    NodeData newdata = new NodeData();
                    newdata.Text = chan.ChName;
                    newdata.Url = "/Channel.aspx?ChId=" + chan.ChId;
                    newdata.Id = chan.ChId;
                    newdata.Type = 1;
                    newdata.ParentId = 0;

                    node.addChild(newdata);// add channels

                    NTree<NodeData> thisChildNode = node.getChild(1); //get this channel node



                    foreach (Zybw.Cms.Addition.Entity.KyColumn kc in chan.KyColumn)
                    {
                        newdata = new NodeData();
                        newdata.Text = kc.ColName;
                        newdata.Url = "/Column.aspx?ColId=" + kc.ColId + "&P=0";
                        newdata.Id = kc.ColId;
                        newdata.Type = 2;
                        newdata.ParentId = thisChildNode.data.Id;

                        thisChildNode.addChild(newdata);// add columns for each channels

                    }

                }
            }
            else if (data.Type == 1)
            {


            }
            else if (data.Type == 2)
            {
                IList<KyColumn> lstCols = GetChildColumns((int)data.Id);
                foreach (KyColumn kc in lstCols)
                {
                    NodeData newdata = new NodeData();
                    newdata.Text = kc.ColName;
                    newdata.Url = "/Column.aspx?ColId=" + kc.ColId + "&P=0";
                    newdata.Id = kc.ColId;
                    newdata.Type = 2;
                    newdata.ParentId = node.data.Id;

                    node.addChild(newdata);// add child columns for each columns


                }
            }


        }



        IList<KyColumn> GetChildColumns(int id)
        {
            IList<KyColumn> lstCol = Zybw.Cms.Addition.Entity.KyColumn.GetByConditon(c => c.ColParentId == id);
            return lstCol;
        }

        protected virtual void CreateNav()
        {
            CreataNavigatorTree();
            TreeVisitor<NodeData> TreeVisitor = NavigatorItemsCreate;
            node.traverse(node, TreeVisitor);

            navBuilder = navBuilder.Replace("channels", channelBuilder.ToString());

            foreach (int key in columCollection.Keys)
            {
                navBuilder = navBuilder.Replace("col" + key.ToString(), columCollection[key]);

            }

            //Add css
            System.Web.UI.Page page = System.Web.HttpContext.Current.Handler as System.Web.UI.Page;
            string css = "<link  href=\"" + page.Request.ApplicationPath + "nav/css/nav.css\"  type=\"text/css\"  rel=\"stylesheet\" />";
            navBuilder.Append(css, 0, css.Length);


            _nav = navBuilder.ToString();

            //remove none columns
            string sPattern = "col\\d{1}";
            System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex(sPattern);
            _nav = reg.Replace(_nav, "");
        }

        string _nav = null;

        public string Nav
        {
            get
            {
                CreateNav();
                return _nav;
            }

        }
        StringBuilder navBuilder = new StringBuilder();
        StringBuilder channelBuilder = new StringBuilder();
        Dictionary<Int32, string> columCollection = new Dictionary<Int32, string>();

        void NavigatorItemsCreate<T>(T TNode)
        {

            NodeData data = TNode as NodeData;

            switch (data.Type)
            {
                case 0:
                    navBuilder.AppendFormat("<div class=\"menu\"><ul>channels</ul></div>");
                    break;
                case 1:

                    channelBuilder.AppendFormat("<li><a class=\"drop\" href=\"{0}\">{1}<!--[if IE 7]><!--></a><!--<![endif]--><table><tr><td><ul>col{2}</li></ul></td></tr></table><!--[if lte IE 6]></a><![endif]-->", data.Url, data.Text, data.Id.ToString());
                    break;
                case 2:
                    StringBuilder level1Builder = new StringBuilder();
                    level1Builder.AppendFormat("<li><a href=\"{0}\" title=\"{1}\">{2}</a></li>", new string[3] { data.Url, data.Text, data.Text });

                    if (columCollection.Keys.Where(c => c == data.ParentId).Count() != 1)
                        columCollection.Add((int)data.ParentId, level1Builder.ToString());
                    else
                        columCollection[(int)data.ParentId] = columCollection[(int)data.ParentId] + level1Builder.ToString();
                    break;
            }




        }




    }