Protected Sub Convailda_Click(sender As Object, e As EventArgs) Handles Convailda.Click

        Dim Elementivalidati As Boolean = False
            'Dim StrNomeCartella As String = "~/Temp/RinnovoPro/" & Now.ToString("HH_mm_ss") & "/"
            For Each riga As GridViewRow In GridView1.Rows
            Dim ChbConvalida As WebControls.CheckBox = riga.FindControl("ChbConvalida")
            If ChbConvalida.Checked Then
                Dim HdnValidation As WebControls.HiddenField = riga.FindControl("HdnValidation")
                Dim IdAllievi As Integer = HdnValidation.Value
                Dim IdProfessional As Integer = HdnValidation.Value
                'GeneraPDF(IdAllievi, StrNomeCartella)
                Elementivalidati = True
                Dim queryString As String = "UPDATE  V_StampaRinnovoPro set Convalida = 1 WHERE IdAllievi = " & IdAllievi
                Dim cmd As New SqlCommand(queryString, conn)
                conn.Open()
                cmd.ExecuteNonQuery()
                conn.Close()
            End If
        Next


    End Sub

 <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="VRinnovoProf" AllowPaging="True" PageSize="24">
                     <PagerSettings Position="Bottom" FirstPageText="<<" LastPageText=">>" Mode="NumericFirstLast" />
        <Columns>
            <asp:BoundField DataField="IdAllievi" HeaderText="ID" SortExpression="IdAllievi" />
            <asp:BoundField DataField="FotoTessera" HeaderText="Photo" SortExpression="FotoTessera" />
            <asp:BoundField DataField="P_Cognome" HeaderText="Surname" SortExpression="P_Cognome" />
            <asp:BoundField DataField="P_Nome" HeaderText="Name" SortExpression="P_Nome" />
            <asp:BoundField DataField="P_DataNascita" HeaderText="Birthdate" SortExpression="P_DataNascita" DataFormatString="{0:d}" />
            <asp:BoundField DataField="AcrBrevetto" HeaderText="Acronym" SortExpression="AcrBrevetto" />
            <asp:BoundField DataField="Descrizione" HeaderText="Certification" SortExpression="Descrizione" />
            <asp:BoundField DataField="DataConvalida" HeaderText="Validation date" SortExpression="DataConvalida" DataFormatString="{0:d}" />
            <asp:BoundField DataField="IdTrainer" HeaderText="IdTrainer" SortExpression="IdTrainer" Visible="false"/> 
            <asp:TemplateField HeaderText="Trainer" SortExpression="CognomeTrainer">
                <EditItemTemplate>
                    <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("CognomeTrainer")%>'></asp:TextBox>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("CognomeTrainer")%>'></asp:Label>
                    <br />
                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("NomeTrainer")%>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField DataField="NomeTrainer" HeaderText="NomeTrainer" SortExpression="NomeTrainer" Visible="False" />
            <asp:BoundField DataField="SiglaBrevTrainer" HeaderText="AcroTrainer" SortExpression="SiglaBrevTrainer" />
            <asp:BoundField DataField="RagioneSociale" HeaderText="EsaPoint" SortExpression="RagioneSociale" />
            <asp:BoundField DataField="DataRinnovo" HeaderText="Renewal date" SortExpression="DataRinnovo" DataFormatString="{0:d}" />
            <asp:BoundField DataField="AnnoRinnovo" HeaderText="Renewal year" SortExpression="AnnoRinnovo" />
            <asp:BoundField DataField="IdRinnovoPro" HeaderText="IdRinnovoPro" ReadOnly="True" SortExpression="IdRinnovoPro" Visible="False" />
            <asp:BoundField DataField="IdBrevetto" HeaderText="IBbrevetto" SortExpression="IdBrevetto" Visible="False" />
            <asp:BoundField DataField="IDEsaPoint" HeaderText="idesapoint" SortExpression="IDEsaPoint" Visible="False" />
             <asp:TemplateField HeaderText="SelezionaStampa" ShowHeader="false" Visible="False">
                                        <ItemTemplate>
                                            <asp:HiddenField ID="HdnIdRinnovoPro" runat="server" value='<%#Eval("IdRinnovoPro")%>' />
                                            <asp:CheckBox ID="chbSelected" runat="server" Visible="false"/>
                                        </ItemTemplate>
                                    </asp:TemplateField>               
            
 <asp:TemplateField HeaderText="Validation">
     <ItemTemplate>
         <asp:HiddenField ID="HdnValidation" runat="server" Value='<%#Eval("IdAllievi") %>' />
     <asp:CheckBox ID="ChbConvalida" runat="server" />
         </ItemTemplate>
 </asp:TemplateField>