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 List<Pt_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).ToList<Pt_OrderWorkFlow>(); 
return rs.Count() > 0 ? rs : new List<Pt_OrderWorkFlow>();