<asp:GridView ID="gvUser" DataKeyNames="ID_User" CssClass="Testo" runat="server" AutoGenerateColumns="False" Width="100%" GridLines="Horizontal" AllowSorting="True" EmptyDataText="Nessun dato presente secondo i criteri di ricerca indicati" EmptyDataRowStyle-Font-Bold="true">
  <Columns>
    <asp:ButtonField Text='<img alt="" src="images/search.gif" style="border:0" />' CommandName="Show"></asp:ButtonField>                
    <asp:BoundField DataField="Titolo" HeaderText="Titolo"  SortExpression="Titolo" />
    <asp:BoundField DataField="Cognome" HeaderText="Cognome" SortExpression="Cognome" />
    <asp:BoundField DataField="Nome" HeaderText="Nome" SortExpression="Nome" />
  </Columns>
</GridView>