DropDownlist显示树状

啥都不说，直接上码...

 /// <summary>
    /// 绑定树视图
    /// </summary>
    /// <param name="dt">数据源</param>
    private void BindTreeView(DataTable dt)
    {
        ddlCategorys.Items.Clear(); //清除数据
        ddlCategorys.Items.Add(new ListItem("全部", "0"));
        if (dt != null && dt.Rows.Count > 0)
        {
            DataRow[] nodeList = dt.Select("ParentID='0'");
            for (int i = 0; i < nodeList.Length; i++)
            {
                ddlCategorys.Items.Add(new ListItem(nodeList[i][ddlCategorys.DataTextField].ToString(), nodeList[i][ddlCategorys.DataValueField].ToString()));
                BindChildNode(dt, nodeList[i][ddlCategorys.DataValueField].ToString());
            }
        }
    }

    /// <summary>
    /// 绑定子节点
    /// </summary>
    /// <param name="dt">数据源</param>
    /// <param name="parentValue">父值</param>
    /// <param name="strBlank">分隔符</param>
    private void BindChildNode(DataTable dt, string parentValue)
    {
        DataRow[] nodeList = dt.Select(string.Format(" {0} = '{1}' ", "ParentID", parentValue));
        for (int i = 0; i < nodeList.Length; i++)
        {
            string strBlank = StringOfChar(int.Parse(nodeList[i]["Level"].ToString()), "&nbsp;&nbsp;");
            ddlCategorys.Items.Add(new ListItem(HttpUtility.HtmlDecode(strBlank) + nodeList[i][ddlCategorys.DataTextField].ToString(), nodeList[i][ddlCategorys.DataValueField].ToString()));
            BindChildNode(dt, nodeList[i][ddlCategorys.DataValueField].ToString());
        }
    }

    private string StringOfChar(int strLong, string str)
    {
        string ReturnStr = string.Empty;
        if (strLong > 1)
        {
            for (int i = 1; i < strLong; i++)
            {
                ReturnStr += str;
            }
            ReturnStr += "├";
        }
        return ReturnStr;
    }

 效果图：

 数据源表结构：