<asp:TemplateField>
            <ItemTemplate>
                <asp:HyperLink ID="link" runat="server" NavigateUrl='<%# "~/Public/Circolari/" + Eval("NomeFile").ToString() %>'><asp:Image ID="img" runat="server" ImageUrl="~/PathImmagine.gif" /></asp:HyperLink>                        
            </ItemTemplate>
        </asp:TemplateField>