遍历节点
void GetAllNodeText(TreeNodeCollection tnc)
{
 foreach(TreeNode node in tnc)
 {
  if(node.Nodes.Count!=0)
   GetAllNodeText(node.Nodes);
  Response.Write(node.Text + " ");
 }
}

建树
private void CreateTree(TreeNodeCollection folderTreeNodeCollection , string parentID)
{
  if (parentID=="")
  {
    dv.RowFilter= "ParentID is null";
  }
  else
  {
    dv.RowFilter= "ParentID="+"'"+parentID+"'";
  }
  foreach (DataRowView drv in dv)
  {
    TreeNode tn= new TreeNode();
    tn.Expanded= true ;
    tn.ID=drv.Row["TypeID"].ToString().Trim();
    tn.Text=drv.Row["TypeName"].ToString().Trim();
    folderTreeNodeCollection.Add(tn);
    CreateTree(tn.Nodes,tn.ID);
  }
}

遍历选中节点
private void getAllCheckedNode(TreeNodeCollection tnc)
{
  foreach (TreeNode tn in tnc)
  {
    if (tn.Checked== true )
    {
      Response.Write(tn.Text+””);
    }
    if (tn.Nodes.Count>0)
    {
      getAllCheckedNode(tn.Nodes);
    }
  }
}

选中或取消选中节点 , 自动选中或取消选中期子节点
private void CheckedChildNode(TreeNode tn)
{
  if (tn.Nodes.Count>0)
  {
    foreach (TreeNode tnn in tn.Nodes)
    {
      tnn.Checked=tn.Checked;
      CheckedChildNode(tnn);
    }
  }
}

调用方法
private void TreeView1_Check( object sender, Microsoft.Web.UI.WebControls.TreeViewClickEventArgs e)
{
    setAllCheckedNode(TreeView1.GetNodeFromIndex(e.Node));
}
1、全部读取并一次性展现

           private void Page_Load(object sender, System.EventArgs e)

           {

                if(IsPostBack)

                {

                     return;

                }

                DBSystem.ExecuteSQL tmp = new DBSystem.ExecuteSQL("T");

                DataTable dt = tmp.GetDataTable("select * from TreeView");//从数据库抓出数据

                this.AddNodes(dt,null,"0");   //添加节点

                this.TreeView1.SelectedNodeIndex="";   //不选中任何节点。

/*下一节将介绍如何修改TreeView.cs 源码来取消默认选中节点的方法*/