private void maketree(datatable dtnodesets, string strparentcolumn, string strrootvalue, string strindexcolumn, string strtextcolumn, dropdownlist drpbind, int i)
{
//每向下一層，多一個縮入單位   
i++;
dataview dvnodesets = new dataview(dtnodesets);
dvnodesets.rowfilter = strparentcolumn + "=" + strrootvalue;
string strpading = ""; //縮入字符  
//通過i來控制縮入字符的長度，我這里設定的是一個全角的空格   
for (int j = 0; j < i; j++)
strpading += "　";//如果要增加縮入的長度，改成兩個全角的空格就可以了  
foreach (datarowview drv in dvnodesets)
{
treenode tnnode = new treenode();
listitem li = new listitem(strpading + "├" + drv[strtextcolumn].tostring(), drv[strindexcolumn].tostring());
drpbind.items.add(li);
maketree(dtnodesets, strparentcolumn, drv[strindexcolumn].tostring(), strindexcolumn, strtextcolumn, drpbind, i);
}
//遞歸結束，要回到上一層，所以縮入量減少一個單位   
i--;
}
/// <summary>   
/// sql語句查詢，再綁定到droplist里面   
/// </summary>   
private void createtree()
{
//查詢zonelist   
string sql = "select * from master_department where parent_department='003'";
dataset ds = db.getds();
datatable dt = ds.tables[0];
maketree(dt, "parent_department", "003", "department_code", "department_name", dropdownlist1, -1);
}

using system;
using system.collections.generic;
using system.text;
using system.web.ui.webcontrols;
namespace interface.common
{
    public interface idropdowntree : idisposable
    {
        /**//// <summary>
        /// 返回dictionary里分別對應id,文本,如果沒有子節點返回null
        /// </summary>
        /// <param name="parentid">父節點id</param>
        /// <returns></returns>
        dictionary<string, string> getchildcategory(string parentid);
        /**//// <summary>
        /// 代碼里寫return new interface.common.dropdowntree(this);
        /// </summary>
        dropdowntree dropdowntree
        {
            get;
        }
    }
    public sealed class dropdowntree
    {
        idropdowntree _dropdowntree;
        public dropdowntree(idropdowntree dropdowntree)
        {
            _dropdowntree = dropdowntree;
        }
        /**//// <summary>
        /// 用于樹的前綴
        /// </summary>
        /// <param name="islast">是否是同級節點中的最后一個</param>
        /// <param name="haschild">本節點是否擁有子節點</param>
        /// <param name="parentstring">父節點前綴符號</param>
        /// <returns>本節點的前綴</returns>
        private string getprefix(bool islast, bool haschild, string parentstring)
        {
            string result = string.empty;
            if (!string.isnullorempty(parentstring))
            {
                parentstring = parentstring.remove(parentstring.length - 1).replace("├", "│").replace("└", "　");
                result += parentstring;
            }
            if (islast)
            {
                result += "└";
            }
            else
            {
                result += "├";
            }
            if (haschild)
            {
                result += "┬";
            }
            else
            {
                result += "─";
            }
            return result;
        }
        綁定下拉菜單#region 綁定下拉菜單
        /**//// <summary>
        /// 綁定連動級的下拉菜單
        /// </summary>
        /// <param name="ddlgoodstype">傳進一個被綁定的dropdownlist</param>
        /// <param name="removeid">被排除綁定的節點id</param>
        /// <param name="autodispose">是否自動釋放</param>
        public void bindtodropdownlist(dropdownlist ddlgoodstype, string removeid,string parentid, bool autodispose)
        {
            if (ddlgoodstype != null)
            {
                listitem listitem = null;
                string currentid = parentid;//根節點/父id
                string currentsign = string.empty;//當前節點符號;
                string parrentsign = string.empty; //父節點符號;
                bool haschild = true;//是否有子
                queue<string> parentkeylist = new queue<string>();//存 有子節點的 節點id
                queue<string> parentsignlist = new queue<string>();//對應節點id的前綴符號
                int itemindexof = 0;//父節點所在的位置　
                while (haschild)
                {
                    int lastonecount = 1;//用于計算在同級別中是否最后一個
                    dictionary<string, string> childlist = _dropdowntree.getchildcategory(currentid);// 得到子節點列表
                    if (childlist != null && childlist.count > 0)
                    {
                        if (!string.isnullorempty(removeid) && childlist.containskey(removeid))
                        {
                            childlist.remove(removeid);
                        }
                        foreach (keyvaluepair<string, string> entry in childlist)
                        {
                            if (_dropdowntree.getchildcategory(entry.key) != null)//存在子
                            {
                                currentsign = getprefix(lastonecount == childlist.count, true, parrentsign);
                                listitem = new listitem(currentsign + entry.value, entry.key);
                                parentkeylist.enqueue(entry.key);//當前的節點id
                                parentsignlist.enqueue(currentsign);//當前的節點符號
                            }
                            else//不存在子
                            {
                                currentsign = getprefix(lastonecount == childlist.count, false, parrentsign);
                                listitem = new listitem(currentsign + entry.value, entry.key);
                            }
                            if (ddlgoodstype.items.count != 0)
                            {
                                itemindexof = string.isnullorempty(currentid) ? itemindexof + 1 : ddlgoodstype.items.indexof(ddlgoodstype.items.findbyvalue(currentid)) + lastonecount;
                            }
                            ddlgoodstype.items.insert(itemindexof, listitem);//添加子節點
                            lastonecount++;
                        }
                        if (parentkeylist.count > 0)//存在子節點時
                        {
                            currentid = parentkeylist.dequeue();
                            parrentsign = parentsignlist.dequeue();
                        }
                        else
                        {
                            haschild = false;
                        }
                    }
                    else
                    {
                        break;
                    }
                }
                if (autodispose)
                {
                    _dropdowntree.dispose();
                }
            }
        }
        /**//// <summary>
        /// 綁定連動級的下拉菜單
        /// </summary>
        /// <param name="ddlgoodstype">傳進一個被綁定的dropdownlist</param>
        public void bindtodropdownlist(dropdownlist ddlgoodstype)
        {
            bindtodropdownlist(ddlgoodstype, string.empty,null, true);
        }
        /**//// <summary>
        /// 綁定連動級的下拉菜單
        /// </summary>
        /// <param name="ddlgoodstype">傳進一個被綁定的dropdownlist</param>
        /// <param name="removeid">被排除的id</param>
        public void bindtodropdownlist(dropdownlist ddlgoodstype, string removeid)
        {
            bindtodropdownlist(ddlgoodstype, removeid,null, true);
        }
        /**//// <summary>
        /// 綁定連動級的下拉菜單
        /// </summary>
        /// <param name="ddlgoodstype">傳進一個被綁定的dropdownlist</param>
        /// <param name="removeid">被排除的id,若沒有,傳null</param>
        /// <param name="parentid">起始父id</param>
        public void bindtodropdownlist(dropdownlist ddlgoodstype, string removeid,string parentid)
        {
            bindtodropdownlist(ddlgoodstype, removeid,parentid, true);
        }
        #endregion
    }
}

idropdowntree 成員
#region idropdowntree 成員
public dictionary<string, string> getchildcategory(string parentid)
{
    string where = "parentid='" + parentid + "'";
    if (string.isnullorempty(parentid))
    {
 where = "parentid is null or parentid='" + guid.empty + "'";
    }
    list<goodscategorybean> _goodscategorylist = selectlist(0, where, string.empty, false);
    if (_goodscategorylist != null && _goodscategorylist.count > 0)
    {
 dictionary<string, string> categorylist = new dictionary<string, string>();
 for (int i = 0; i < _goodscategorylist.count; i++)
 {
     categorylist.add(_goodscategorylist[i].id.tostring(), _goodscategorylist[i].gategoryname);
 }
 return categorylist;
    }//51aspx.com
    return null;
}
public interface.common.dropdowntree dropdowntree
{
    get { return new interface.common.dropdowntree(this); }
}
#endregion