BLL.DAL.表现层作用

bll是业务逻辑层。并不只是调用dal传递数据的作用。你可以这样理解。dal它只是取数据。然后你前台要的数据并不是你从dal层取到数据。还需要一些处理才是表现层所需要的数据。这个处理的过程就是由bll来处理的。你可能会可以放在表现层处理。是的，是可以的。但是那就不能体现三层架构的意义了。

dal:
/// <summary>
        /// 获取下级栏目列表
        /// </summary>
        /// <param name="id">栏目ID</param>
        /// <returns>Column对象</returns>
        public static DataTable GetChildList(int id)
        {
            return DBHelper.GetData(string.Format("select * from [column] where parentid = {0} order by sort" , id));
        }
BLL:
  /// <summary>
        ///  递归遍历父节点所有子节点
        /// </summary>
        public static IList<Column> GetList(IList<Column> list, int pid, int n)
        {
            DataTable dt = ColumnAgent.GetChildList(pid);
            if (dt == null) return null;
            if (dt.Rows.Count == 0)
            {
                return null;
            }
            else
            {
                foreach (DataRow dr in dt.Rows)
                {
                    Column column = new Column();
                    column.ID = int.Parse(dr["ID"].ToString());
                    if (pid == 0)
                    {
                        column.ChName = dr["ChName"].ToString() + "(" + dr["EnName"].ToString() + ")"; ;
                    }
                    else
                    {
                        column.ChName = "├".PadLeft(n, ' ') + dr["ChName"].ToString() + "(" + dr["EnName"].ToString() + ")";
                    }
                    column.ChPic = dr["ChPic"].ToString();
                    column.EnName = dr["EnName"].ToString();
                    column.ChLink = dr["ChLink"].ToString();
                    column.EnLink = dr["EnLink"].ToString();
                    column.ParentID = int.Parse(dr["ParentID"].ToString());
                    column.Navigate = int.Parse(dr["Navigate"].ToString());
                    list.Add(column);
                    n = n + 1;
                    GetList(list, column.ID, n);
                    n = n - 1;
                }
                return list;
            }

        }
在dal中我们只是获取数据，不用处理它
到bll中我们要把它处理成我们表现层所需要的