用递归无限级绑定 treeview,DropDownList

表结构，id ,Parentid

TreeView:

public void bind()
  {
   TreeNode no=new TreeNode();
   no.Expanded = true;
   TreeView2.Nodes.Add(no);
   no.Text = "所有文章类型";
   CreateTree("0", no);
  }
  private void CreateTree(string belong,TreeNode rootnode)
  {
//   SqlConnection connString = new SqlConnection("server=192.168.2.9;uid=sa;pwd=;database=Bjmti");
   SqlConnection connString = new SqlConnection(ConfigurationSettings.AppSettings["ConnStr"].ToString());
   SqlCommand command = new SqlCommand("Select * FROM school_Menu where W_ParentID='"+belong+"'", connString);
   SqlDataAdapter adapter = new SqlDataAdapter(command);
   DataSet ds = new DataSet();
   adapter.Fill(ds);
   foreach(DataRow dr in ds.Tables[0].Rows)
   {
    TreeNode treenode = new TreeNode();
    treenode.Text = dr["W_Name"].ToString().Trim();
    treenode.Expanded = true;
    rootnode.Nodes.Add(treenode);
    string id = dr["W_ID"].ToString().Trim();
    treenode.NavigateUrl="Bjmti_ArticleShow_List.aspx?ID="+dr["W_ID"].ToString()+"";
    CreateTree(id, treenode);
   }
  } 

DropDownList:

private void GetArticleCategory(string pid)
  {
   string strSpGroup = "Bjmti_KD_Ken_SEL_Group";
   SqlParameter[] spParamGroup = new SqlParameter[1];   
   spParamGroup[0] =new SqlParameter("@KD_ParentID",SqlDbType.VarChar,36);
   spParamGroup[0].Value=pid;
            DataSet ds= DbHelperSQL.BjmtiDataSet(strSpGroup,spParamGroup);
     foreach(DataRow row in ds.Tables[0].Rows) 
     {
    this.ddlKl.Items.Add(new ListItem(toadd + " " + row["KD_Name"].ToString(),row["KD_ID"].ToString()));
    toadd += "─┴";
    this.GetArticleCategory(row["KD_ID"].ToString());
    toadd = toadd.Substring(0, toadd.Length - 2);  //处理层次关系显示
   }
  }