DropDownList實現樹形結構顯示

轉自：http://hi.baidu.com/wf225/blog/item/f0e25a6659f31924aa184c60.html

public System.Web.UI.WebControls.DropDownList  AddDropDownList  (System.Web.UI.WebControls.DropDownList droplist, int ParentID, ListItem plist)
        {
            string NodeId = "ID";
            string ParentId = "ParentId";
            string NodeName = "Name";

            //DataSet dsFlowType = myData.GetFlowTypeDS();
            DataView dvTree = new DataView(dsFlowType.Tables[0]);

            //過濾ParentId,得到當前的所有子節點
            dvTree.RowFilter = ParentId + " = " + ParentID.ToString();
            foreach (DataRowView drv in dvTree)
            {
                //-----------------------------------------
                int depth = 0;
                int NodeID = Convert.ToInt32(drv[NodeId]); ;
                Depth(NodeID, ref depth);   //計算當前節點深度

                string blank = "";
                if (ParentID != 0)
                {
                    for (int i = 1; i <= depth; i++)
                    {
                        blank += "|－";
                    }
                }
                //-----------------------------------------
                ListItem list = new ListItem();
                list.Text = blank + drv[NodeName].ToString().Trim();
                list.Value = drv[NodeId].ToString().Trim();
                droplist.Items.Add(list);       //***注意區別:根節點
                AddDropDownList(droplist, Int32.Parse(drv[NodeId].ToString().Trim()), list);    //遞迴

            }
            return droplist;
        }
        //計算當前節點深度
        public int Depth(int NodeID, ref int depth)
        {
            string NodeId = "ID";
            string ParentId = "ParentId";

            //DataSet dsFlowType = myData.GetFlowTypeDS();
            DataView dvTree = new DataView(dsFlowType.Tables[0]);
            //過濾ParentId,得到當前的所有父節點
            dvTree.RowFilter = NodeId + " = " + NodeID.ToString();
            foreach (DataRowView drv in dvTree)
            {
                int ID = Convert.ToInt32(drv[ParentId]);
                if (ID != 0)
                {
                    depth += 1;
                    Depth(ID, ref depth);    //遞迴
                }
            }
            return depth;
        }