DropdownList无限极显示 怎么没有效果

Question

我下面的这种做法在用SQL2005可以 显示效果但如果是ACCESS就不能显示效果
我现在要用ACCESS  我该怎么处理这个问题  
protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            BindMain();        }
    }
    void GD()
    {
      DataTable dt = db.ReturnDataTable();
      DropDownList1.Items.Clear();
       DropDownList1.Items.Add(new ListItem("---","0"));
        DataRow[] drs=dt.Select("CarID="+0);
        foreach (DataRow dr in drs)
      {
          string classid = dr["ID"].ToString();
       string classname = dr["CarKindName"].ToString();
           //顶级分类显示形式
        classname = "____" + classname;
           DropDownList1.Items.Add(new ListItem(classname,classid));         int sonparentid = int.Parse(classid);
           string blank = "____";
           BindNode(sonparentid,dt,blank);
        DropDownList1.DataBind();       }
   }
    private void BindNode(int parentid, DataTable dt, string blank)
   {
        DataRow[] drs = dt.Select("CarID=" + parentid);
      foreach( DataRow dr in drs )
        {
        string classid = dr["ID"].ToString();
          string classname = dr["CarKindName"].ToString();          classname = blank + classname;
           DropDownList1.Items.Add(new ListItem(classname,classid));
          int sonparentid = int.Parse(classid);
            string blank2 = blank + "____";           BindNode(sonparentid, dt, blank2);
        }
    }
DAL public static OleDbConnection GetCon()
        {
            return new OleDbConnection(@"PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA Source=UI\App_Data\autoUnion.mdb");
        }
      
       
        public static DataTable ReturnDataTable()
        {
            DataSet ds = new DataSet();
            OleDbConnection strCon = DBcON.GetCon();
            string Sql = "select * from carKindInfo";
            OleDbDataAdapter da = new OleDbDataAdapter(Sql, strCon);
            DataTable dt = new DataTable();
            ds.Tables.Add(dt);            try
            {
                strCon.Open();
                da.Fill(ds, "table");
                return ds.Tables["table"];
            }
            finally
            {
                da = null;
                dt = null;
              
            }
        }

Answer 1

单步调试
public class DDLDepartment : DropDownList
    {
      
        public DDLDepartment()
        {
            this.Items.Insert(0, new ListItem("==请选择==", ""));
        }
        public void bind(DropDownList ddlDepartment, int parent)
        {
            IList<Department> deptlist = DepartmentBLL.SelectChild(parent);
            foreach (Department dept in deptlist)
            {
                string text = new string('　', dept.Depth - 1);
                text += "└" + dept.DeptName;
                ddlDepartment.Items.Add(new ListItem(text, dept.DeptId.ToString()));
                bind(this, dept.DeptNo);
            }
            
        }
    }