下拉框层级绑定

今天用到一个下拉框绑定，要有层级关系显示的，也很简单，就当第一篇博客！

　　　/// <summary>
        /// 绑定下拉框
        /// </summary>
        /// <param name="dt">绑定的数据源</param>
        /// <param name="parentId">上一级的id名称</param>
        /// <param name="colId">值名称</param>
        /// <param name="colName">文本名称</param>
        /// <param name="drs">最上层的记录集合</param>
        /// <param name="ddl">下拉框</param>
        /// <param name="leveStr">层级的前缀</param>
        /// <param name="nextStr">层级的前缀的前缀</param>
        protected void GetChild(DataTable dt, string parentId, string colId, string colName, DataRow[] drs, DropDownList ddl, string leveStr, string nextStr)
        {
            foreach (DataRow dr in drs)
            {
                string txt = dr[colName].ToString();
                if (leveStr.Length != 1)
                {
                    txt = leveStr + dr[colName].ToString();
                }
                ddl.Items.Add(new ListItem(txt, dr[colId].ToString()));
                DataRow[] cdrs = dt.Select(parentId + " ='" + dr[colId] + "'", colId + " asc");
                if (cdrs.Length != 0)
                {
                    string nextLevelStr = leveStr.Insert(0, nextStr);
                    GetChild(dt, parentId, colId, colName, cdrs, ddl, nextLevelStr, nextStr);