树形结构 DropDownList前台 <asp:DropDownList ID="ddlOutType" runat="server" />后台代码： 先绑定第一级按 Ctrl+C 复制代码string SQL = "SELECT CategoryID,CategoryName,ParentID FROM Category" DataTable datatable = SqlHelper.ExecuteDataTable(SQL); DataRow[] row = datatable.Select("ParentID='0'"); //添加根目录 for (int i = 0; i < row.Length; i++) { ListItem li = new ListItem(row[i]["CategoryName"].ToString(), row[i]["CategoryID"].ToString()); ddlOutType.Items.Add(li); addOtherDll("", Convert.ToInt32(row[i]["CategoryID"]), datatable, 1, ddlOutType); }按 Ctrl+C 复制代码 递归查找下级按 Ctrl+C 复制代码/// <param name="Pading">空格</param> /// <param name="DirId">父路径ID</param> /// <param name="datatable">返回的datatable</param> /// <param name="deep">树形的深度</param> private void addOtherDll(string Pading, int DirId, DataTable datatable, int deep,DropDownList ddl) { DataRow[] rowlist = datatable.Select("ParentID='" + DirId + "'"); foreach (DataRow row in rowlist) { string strPading = ""; for (int j = 0; j < deep; j++) { strPading += " "; //用全角的空格 } //添加节点 ListItem li = new ListItem(strPading + "|--" + row["CategoryName"].ToString(),row["CategoryID"].ToString()); ddl.Items.Add(li); //递归调用addOtherDll函数，在函数中把deep加1 addOtherDll(strPading, Convert.ToInt32(row["CategoryID"]), datatable, deep + 1, ddl); } }按 Ctrl+C 复制代码