<asp:GridView ID="GV_Picking_Ordini" runat="server" 
          DataKeyNames="OS_Anno,OS_Codcen,OS_Coddep,OS_Tipord,OS_Numord,OS_Distinzione"  
          AutoGenerateColumns="False"
          SelectMethod="CodaPickingGetData" ItemType="CODA_PICKING" 
          DeleteMethod="Delete_CODA_PICKING"
          Allowpaging="True"  AllowSorting="True" 
          ...>
...
<asp:TemplateField ShowHeader="False">
                    <ItemTemplate>
                        <asp:LinkButton ID="lnkBtnSelect" runat="server" CausesValidation="False" 
                            OnCommand="lnkBtnSelect_Command"  CommandArgument="<%# Container.DataItemIndex %>"
                            CommandName="Select"  Text="Seleziona">
                        </asp:LinkButton>
                    </ItemTemplate>
                </asp:TemplateField>

 public int NumeroOrdini{
  get{
      using(Entity db = new ...)){
      int nr = db.tab.where(i=>i.stato="chiuso").count();
return nr;
}
}
}