GridView Control to use the ModalPopupExtender Control how to store and update the information in Database

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" AutoGenerateColumns="False"
                            CssClass="grid-view" Font-Names="Calibri" Width="1030px" ForeColor="#333333"
                            PageSize="15" onrowdeleting="GridView1_RowDeleting" 
                            onrowcommand="GridView1_RowCommand" onrowupdating="GridView1_RowUpdating" 
                            onload="GridView1_Load" >
                            <columns>
                                <asp:BoundField HeaderText="S.No" DataField="id" />
                                <asp:BoundField DataField="Date" HeaderText="Date" />
                                <asp:BoundField DataField="ProjectName" HeaderText="Project Name" />
                                <asp:BoundField DataField="GrandTotal" HeaderText="Gross Total" />
                                <asp:TemplateField>
                                    <HeaderTemplate>
                                        Rateing
                                    </HeaderTemplate>
                                    <itemtemplate>
                                        <asp:Button ID="Gdvwratebtn" runat="server" Text="Rate **" CssClass="allbutton"  />
                                        <asp:Panel ID="ratepopup" runat="server" Style="margin-left: 700px; margin-bottom: 200px;
                                            font-family: Calibri; font-size: 11pt; background-color: White; width: 280px;
                                            height: 140px;">
                                            <center>
                                                <table>
                                                    <tr style="text-align: center;">
                                                        <td colspan="2" style="font-size: 12pt; text-align: center; font-weight: 700;">
                                                            Rateing Purchase Order & Work Order
                                                        </td>
                                                    </tr>
                                                    <tr style="text-align: center;">
                                                        <td>
                                                            Quality :
                                                        </td>
                                                        <td>
                                                            <asp:DropDownList ID="DDLQpop" runat="server">
                                                                <asp:ListItem>1
                                                                <asp:ListItem>2
                                                                <asp:ListItem>3
                                                                <asp:ListItem>4
                                                                <asp:ListItem>5
                                                                <asp:ListItem>6
                                                                <asp:ListItem>7
                                                                <asp:ListItem>8
                                                                <asp:ListItem>9
                                                                <asp:ListItem>10
                                                            
                                                        </td>
                                                    </tr>
                                                    <tr style="text-align: center;">
                                                        <td>
                                                            Timing :
                                                        </td>
                                                        <td>
                                                            <asp:DropDownList ID="DDLTpop" runat="server">
                                                                <asp:ListItem>1
                                                                <asp:ListItem>2
                                                                <asp:ListItem>3
                                                                <asp:ListItem>4
                                                                <asp:ListItem>5
                                                                <asp:ListItem>6
                                                                <asp:ListItem>7
                                                                <asp:ListItem>8
                                                                <asp:ListItem>9
                                                                <asp:ListItem>10
                                                            
                                                        </td>
                                                    </tr>
                                                    <tr style="text-align: center;">
                                                        <td>
                                                            Money :
                                                        </td>
                                                        <td>
                                                            <asp:DropDownList ID="DDLMpop" runat="server">
                                                                <asp:ListItem>1
                                                                <asp:ListItem>2
                                                                <asp:ListItem>3
                                                                <asp:ListItem>4
                                                                <asp:ListItem>5
                                                                <asp:ListItem>6
                                                                <asp:ListItem>7
                                                                <asp:ListItem>8
                                                                <asp:ListItem>9
                                                                <asp:ListItem>10
                                                            
                                                        </td>
                                                    </tr>
                                                    <tr style="text-align: center;">
                                                        <td>
                                                            <asp:Button ID="RateSaveBtn" runat="server" Text="Submit Rateing" CssClass="allbutton"
                                                                Width="100px" CommandName="SvePnl"  />
                                                        </td>
                                                        <td>
                                                            <asp:Button ID="RateCancelBtn" runat="server" Text="Cancel" CssClass="allbutton" />
                                                        </td>
                                                    </tr>
                                                </table>
                                            </center>
                                        
                                        <asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="Gdvwratebtn"
                                            BackgroundCssClass="modalBackground" PopupControlID="ratepopup" DropShadow="true">
                                        
                                    </itemtemplate>
                                

                                <asp:ButtonField ButtonType="Button" Text="Button" />

                            </columns>
                            <footerstyle backcolor="Gray" height="15px" />
                            <HeaderStyle BackColor="#013A81" BorderColor="#013A81" BorderStyle="Solid" BorderWidth="1px"
                                Font-Names="Calibri" Font-Size="10pt" ForeColor="White" VerticalAlign="Middle" />
                            <SelectedRowStyle BackColor="#333333" ForeColor="White" />