datagrid绑定list没有数据 表头不显示的解决方法

var list = Pt_OrderWorkFlow_DAO.GetOrderWorkFlow(wfid, uid, 1);
         if (list == null)
         {
             list = new ListPt_OrderWorkFlow>();
         }
         dgWaitList.DataSource = list;
         dgWaitList.DataBind();

OADataContext db = DatabaseHelper.GetDB();
var rs = (from a in db.Pt_OrderWorkFlow
          where a.WFID == wfID a.ContractNumber == cNumber 
          select a).ToListPt_OrderWorkFlow>();
return rs.Count() > 0 ? rs : new ListPt_OrderWorkFlow>();