varunmaggo's say

Go to your aspx web form and try this

<asp:DataList ID="dlContacts" runat="server">
<ItemTemplate>

<!-- Add your Item Template Here -->

</ItemTemplate>
<FooterTemplate>
<asp:Label ID="lblEmpty" Text="no result" runat="server"
     Visible='<%#bool.Parse((dlContacts.Items.Count==0).ToString())%>'>
</asp:Label>
</FooterTemplate>
</asp:DataList>

For GridView:

 <EmptyDataTemplate>
  <table border="0px" cellpadding="5" cellspacing="5">
   <tr><td>
       Error Message here!
      </td>
   </tr>
  </table>
 </EmptyDataTemplate>
 <EmptyDataRowStyle CssClass="empty" ForeColor="Red" />