DataBinder.Eval(i.DataItem, "Title")未将对象引用设置到对象的实例异常

   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            }        }