foreach (RepeaterItem i in List.Items)
        {

            CheckBox cb = (CheckBox)i.FindControl("Select");
            HiddenField hd = (HiddenField)i.FindControl("hfCode");           
            bool matter = cb.Checked;
            if (matter)
            {
                  //出现错误 Response.Write(DataBinder.Eval(i.DataItem, "Title").ToString()+"<br/>");
                 Response.Write(hd.Value + "<br/>"); //这种方式成功
            }
        }