在做datalist分页功能时，设的转页按钮组（linkbutton）无效，是咋回事

 protected void Page_Load(object sender, EventArgs e)    {        if (!IsPostBack)         DataList1_content(); //数据绑定datalist     }    private void DataList1_content()  //分页    {        PagedDataSource ps = new PagedDataSource();//分页实例        DataTable dt2 = new InnerBLL().SelectAll();        ps.DataSource = dt2.DefaultView;//绑定分页        ps.AllowPaging = true; //允许分页        ps.PageSize = 10;//每页条数        int maxpage;//总共多少页        if (ps.Count == 0) return;        if (ps.DataSourceCount % ps.PageSize > 0)//计算总页数        {            maxpage = ps.DataSourceCount / ps.PageSize + 1;//有余数要加1        }        else { maxpage = ps.DataSourceCount / ps.PageSize; }        Session["maxpage"] = maxpage;//保存总页数，在翻页判断时使用        int curpage;//当前页码        if (Session["curpage"] == null)        {            curpage = 1;//初始化页码        }        else { curpage = Convert.ToInt32(Session["curpage"]); }        Session["curpage"] = ps.CurrentPageIndex + 1;//页码        lblpage.Text = "第" + Session["curpage"].ToString() + "页（共" + Session["maxpage"].ToString() + "页）";//lable标签        DataList1.DataSource = ps;        DataList1.DataBind();    }    public void PagerButtonClick(object sender, EventArgs e)  //LinkButton组    {            case "next":                      if (curpage < Convert.ToInt32(Session["maxpage"]))//未到末页                    {                        curpage = curpage + 1;                    } break;                case "prev":                    if (curpage > 1)//未到首页                    {                        curpage = curpage - 1;                    } break;               case "last":                    curpage = Convert.ToInt32(Session["maxpage"]); break;            default:             curpage = 1; break;        }        Session["curpage"] = curpage;        DataList1_content();    }

            <asp:Label ID="lblpage" runat="server" ></asp:Label>            <asp:LinkButton ID="lb1" runat="server" CommandArgument="fir" >首页</asp:LinkButton>            <asp:LinkButton ID="lb2" runat="server" CommandArgument="prev">上一页</asp:LinkButton>            <asp:LinkButton ID="lb3" runat="server" CommandArgument="next">下一页</asp:LinkButton>            <asp:LinkButton ID="lb4" runat="server" CommandArgument="last">末页</asp:LinkButton>