<asp:GridView ID="GridView1" runat="server" AllowPaging="True" PageSize="25" CssClass="campiform" AllowSorting="True" AutoGenerateColumns="False" DataKeyNames="id_utente" DataSourceID="SqlDataSource1">
                        <Columns>
                            <asp:BoundField DataField="cognome" HeaderText="Cognome" SortExpression="cognome" />
                            <asp:BoundField DataField="nome" HeaderText="Nome" SortExpression="nome" />
                            <asp:BoundField DataField="username" HeaderText="Username" SortExpression="username" />
                            <asp:BoundField DataField="password" HeaderText="Password" SortExpression="password" />
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:ImageButton ID="modifica" runat="server" ImageUrl="~/images/pencil.gif" OnClick="modifica_Click" />
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:ImageButton ID="visualizza" runat="server" ImageUrl="~/images/lens.gif" OnClick="visualizza_Click" />
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:Button ID="cancella" runat="server" Text="Cancella" OnClick="cancella_Click" />
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView> 
            <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
                        ConnectionString="<%$ ConnectionStrings:itemsConnectionString %>" 
                        SelectCommand="select * from utenti where acconsento=1 order by cognome">
                    </asp:SqlDataSource>