请问SQL Server Management Studio 2005 中，打开树节点时边加载边显示(Expanding...)的效果是如何实现的？

public partial class Form1 : Form

    {

        class TreeNodeEx : TreeNode

        {

            public TreeNodeEx(string text)

                : base(text)

            {

            }



            //用来控制节点是否已经打开过

            private bool opened = false;

            public bool Opened

            {

                get { return opened; }

                set { opened = value; }

            }

        }



        //添加节点的代理

        private delegate void AddNodeDelegate(TreeNode root, string childText);

        private AddNodeDelegate myAddNode = null;



        //修改节点名称的代理

        private delegate void AlterTreeNodeText(string text);

        private AlterTreeNodeText alterTreeNodeText = null;



        //当前选择的节点

        TreeNodeEx currentSelectedNode = null;

        string oldValue;



        public Form1()

        {

            InitializeComponent();

            TreeNodeEx n = new TreeNodeEx("1");

            n.

            this.treeView1.Nodes.Add(new TreeNodeEx("1"));

            this.treeView1.Nodes.Add(new TreeNodeEx("2"));



            alterTreeNodeText = new AlterTreeNodeText(this.OnAlterTreeNodeText);

            myAddNode = new AddNodeDelegate(this.AddNodes);

        }



        protected void OnAlterTreeNodeText(string text)

        {

            if (currentSelectedNode != null)

                currentSelectedNode.Text = text;

        }

        private void AddNodes(TreeNode node, string text)

        {

            node.Expand();

            node.Nodes.Add(new TreeNodeEx(text));

        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)

        {

            TreeNodeEx node = e.Argument as TreeNodeEx;

            if (node == null) return;



            oldValue = node.Text;

            string newValue = string.Concat(oldValue, "(Expanding...)");

            BeginInvoke(alterTreeNodeText, new object[] { newValue });



            for (int i = 1; i <= 50; i++)

            {

                IAsyncResult ar = BeginInvoke(myAddNode, new object[] { node, i.ToString() });

                // 等待添加完毕

                while (!ar.IsCompleted)

                {

                    Thread.Sleep(100);

                    Application.DoEvents();

                    ar.AsyncWaitHandle.WaitOne(-1, false);

                }

            }

        }



        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

        {

            BeginInvoke(alterTreeNodeText, new object[] { oldValue });

            currentSelectedNode.Opened = true;

        }

 

        private void treeView1_BeforeExpand(object sender, TreeViewCancelEventArgs e)

        {

            currentSelectedNode = e.Node as TreeNodeEx;

            if (currentSelectedNode.Opened) return;

            this.backgroundWorker1.RunWorkerAsync(currentSelectedNode);

        }

    }

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;



namespace WindowsApplication11

{

    public partial class Form1 : Form

    {

        public class ThreadStartInfo

        {

            public TreeNode node=null;

            public  void LoadNode()

            {

                System.Threading.Thread.Sleep(5000);

                string[] str = new string[] { "jinjazz", "csdn" };

                this.AddNode(node, str);

            }

            delegate void dAddNode(TreeNode node, string[] str);

            void AddNode(TreeNode node, string[] str)

            {

                if (this.node.TreeView.FindForm().InvokeRequired)

                {

                    this.node.TreeView.FindForm().Invoke(new dAddNode(AddNode), new object[] { node, str });

                }

                else

                {

                    node.Nodes.Clear();

                    foreach (string strNode in str)

                    {

                        node.Nodes.Add(strNode);

                    }

                }



            }

        }



        public Form1()

        {

            InitializeComponent();

        }



        private void Form1_Load(object sender, EventArgs e)

        {

            this.treeView1.Nodes.Add(new TreeNode("root"));

            this.treeView1.AfterSelect += new TreeViewEventHandler(treeView1_AfterSelect);

        }



        void treeView1_AfterSelect(object sender, TreeViewEventArgs e)

        {

            if (e.Node.Tag==null||e.Node.Tag.ToString() == "")

            {

                ThreadStartInfo s = new ThreadStartInfo();

                s.node = e.Node;

                s.node.Tag = 1;

                new System.Threading.Thread(new System.Threading.ThreadStart(s.LoadNode)).Start();

                e.Node.Nodes.Add("正在载入..");

            }

        }



       



       

    }

}