addNode: $.proxy(this.addNode, this), 

 /** 
    给节点添加子节点 
@param {Object|Number} identifiers - A valid node, node id or array of node identifiers 
@param {optional Object} options.node; 
  */ 
Tree.prototype.addNode = function (identifiers, options) { 
  this.forEachIdentifier(identifiers, options, $.proxy(function (node, options) { 
    this.setAddNode(node, options);  
  }, this)); 
  this.setInitialStates({ nodes: this.tree }, 0); 
  this.render(); 
} 
  /** 
  * 添加子节点 
  */ 
Tree.prototype.setAddNode = function (node, options) { 
  if (node.nodes == null) node.nodes = []; 
  if (options.node) { 
    node.nodes.push(options.node); 
  }; 
}; 

$("#Treeview01").treeview("addNode", [2, { node: { text: "新加的菜单", href: "001005" } }]); 

 private void button1_Click(object sender, EventArgs e)
    {
      FolderBrowserDialog fd = new FolderBrowserDialog();
      if (fd.ShowDialog() == DialogResult.OK)
      {
        // 在此添加代码,选择的路径为 folderBrowserDialog1.SelectedPath
        if (Directory.Exists(fd.SelectedPath))
        {
          DirectoryInfo thisOne = new DirectoryInfo(fd.SelectedPath);
          DirectoryInfo[] directoryInfo = thisOne.GetDirectories();
          for (int i = 0; i < directoryInfo.Length; i++)
          {
            TreeNode root = new TreeNode(directoryInfo[i].ToString());//创建节点
            root.Name = directoryInfo[i].ToString(); //为节点取个名字,这儿创建的是根节点
            root.Tag = 0;
            treeView1.Nodes.Add(root);        //将节点添加到treeView1上
            DirectoryInfo thisTwo = new DirectoryInfo(fd.SelectedPath + "\\" + directoryInfo[i].ToString());
            FileInfo[] fileInfo = thisTwo.GetFiles();
            for (int j = 0; j < fileInfo.Length; j++)
            {
              TreeNode node = new TreeNode(fileInfo[j].ToString());
              node.Tag = 1;
              node.Name = fileInfo[j].ToString();
              if (!root.Nodes.ContainsKey(node.Name))
              {
                root.Nodes.Add(node);
              }
            }
          }
        }
      }
    }