ASP.NET如何递归循环所有的分类呢？？

private void ParseClassList()  
  {
  Response.Write(LoopClass(0)); // 只输出第一类的。子类都没有输出来？ 如果循环呢？？
  }  
  private string LoopClass(int classid)
  {
  StringBuilder classlist = new StringBuilder();
  ArticleClassAccesser classAccesser = new ArticleClassAccesser(this.LshopAdminDbAccesser);
  ArticleClassSearchKeyword keyword = new ArticleClassSearchKeyword();
  keyword.ParentID = classid;
  DataElementCollection<ArticleClass> list = classAccesser.List(0, keyword);
  if (list != null)
  {
  foreach (ArticleClass aclass in list)
  {
  classlist = classlist.Append("<tr>");
  classlist = classlist.Append(" <td style=\"width:30px;\"><input type=\"checkbox\" name=\"ids\" value=\"" + aclass.ClassID + "\"/></td>");
  classlist = classlist.Append(" <td>" + aclass.ClassID + "</td>");
  classlist = classlist.Append(" <td>" + aclass.ClassName + "</td>");
  classlist = classlist.Append(" <td>" + aclass.OrderID + "</td>");
  classlist = classlist.Append(" <td>" + aclass.ParentPath + "</td>");
  classlist = classlist.Append(" <td style=\"width:150px;\"><a href=\"ArticleClassInfo.aspx?id=<$:ArticleClassList.Id>\" title=\"修改记录\">修改</a></td>");
  classlist = classlist.Append("</tr>");
  LoopClass(aclass.ClassID); 这里好像不起作用哦，
  }
  }
  return classlist.ToString();
  }