主要使用递归实现，数据库结构：



最终样式：

 

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        BindDrpClass();
    }
}
//绑定顶级分类
private void BindDrpClass()
{
    Bll.Class classSystem = new Bll.Class();
    DataTable dt = classSystem.GetClassList("").Tables[0];
    ddlClass.Items.Clear();
    ddlClass.Items.Add(new ListItem("添加根栏目", "0"));
    DataRow[] drs = dt.Select("ParentID= " + 0);

    foreach (DataRow dr in drs)
    {
        string classid = dr["ClassID"].ToString();
        string classname = dr["ClassName"].ToString();
        //顶级分类显示形式
        classname = "╋" + classname;

        ddlClass.Items.Add(new ListItem(classname, classid));
        int sonparentid = int.Parse(classid);
        string blank = "├";
        //递归子分类方法
        BindNode(sonparentid, dt, blank);
    }
    ddlClass.DataBind();
}
//绑定子分类
private void BindNode(int parentid, DataTable dt, string blank)
{
    DataRow[] drs = dt.Select("ParentID= " + parentid);

    foreach (DataRow dr in drs)
    {
        string classid = dr["ClassID"].ToString();
        string classname = dr["ClassName"].ToString();

        classname = blank + classname;
        ddlClass.Items.Add(new ListItem(classname, classid));

        int sonparentid = int.Parse(classid);
        string blank2 = blank + "─";

        BindNode(sonparentid, dt, blank2);
    }
}
public DataSet GetClassList(string strWhere)
{
    StringBuilder strSql = new StringBuilder();
    strSql.Append("select * from tb_Class ");
    if (strWhere.Trim() != "")
    {
        strSql.Append(" where " + strWhere);
    }
    return SqlHelper.ExecuteDataset(SqlHelper.ConnString, CommandType.Text, strSql.ToString());
}