Hi makumbi,
Please refer below sample code.
Database
For this example I have used of Northwind database that you can
download using the link given below.
Download Northwind Database
HTML
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <div class="container">
        <div class="table-responsive">
            <asp:GridView ID="GridView1" AutoGenerateColumns="False" runat="server" CssClass="table table-bordered table-hover table-striped thead-dark GridCustomers">
                <Columns>
                    <asp:BoundField DataField="CustomerID" HeaderText="Customer ID" />
                    <asp:BoundField DataField="CompanyName" HeaderText="Company Name" />
                    <asp:BoundField DataField="ContactName" HeaderText="Contact Name" />
                    <asp:BoundField DataField="ContactTitle" HeaderText="Contact Title" />
                    <asp:BoundField DataField="Address" HeaderText="Address" />
                    <asp:TemplateField>
                        <ItemTemplate>
                            <asp:LinkButton ID="lnkEdit" runat="server">Edit</asp:LinkButton>
                        </ItemTemplate>
                    </asp:TemplateField>
                </Columns>
            </asp:GridView>
        </div>
    </div>
    <div id="MyPopup" class="modal fade" role="dialog">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal">
                        ×</button>
                    <h4 class="modal-title">
                        Update Payments
                    </h4>
                </div>
                <div class="modal-body">
                    <table class="table table-bordered table-hover table-striped thead-dark">
                        <tr>
                            <td>
                                admno
                            </td>
                            <td>
                                <asp:TextBox runat="server" ID="admno" ReadOnly="true" CssClass="form-control" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                Name
                            </td>
                            <td>
                                <asp:TextBox runat="server" ID="txtName" CssClass="form-control" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                Country
                            </td>
                            <td>
                                <asp:TextBox runat="server" ID="txtCountry" CssClass="form-control" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                Date
                            </td>
                            <td>
                                <asp:TextBox runat="server" ID="Date" CssClass="form-control" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                Cash
                            </td>
                            <td>
                                <asp:TextBox runat="server" ID="Pay" CssClass="form-control" />
                            </td>
                        </tr>
                        <tr>
                            <td>
                                Category
                            </td>
                            <td>
                                <asp:DropDownList ID="Categoryddl" runat="server" CssClass="form-control">
                                    <asp:ListItem>NONE</asp:ListItem>
                                    <asp:ListItem>SATURDAY</asp:ListItem>
                                    <asp:ListItem>CLUBS</asp:ListItem>
                                    <asp:ListItem>TRIPS</asp:ListItem>
                                </asp:DropDownList>
                            </td>
                        </tr>
                    </table>
                </div>
                <div class="modal-footer">
                    <asp:Button ID="btnUpdate" Text="Update" runat="server" CssClass="btn btn-primary"
                        OnClick="OnUpdate" />
                    <input type="button" value="Close" class="btn btn-danger" data-dismiss="modal" />
                </div>
            </div>
        </div>
    </div>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
    <script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
    <script type="text/javascript" src="https://cdn.datatables.net/1.10.20/js/jquery.dataTables.min.js"></script>
    <link href="https://cdn.datatables.net/1.10.20/css/jquery.dataTables.css" rel="stylesheet"
        type="text/css" />
    <script type="text/javascript">
        $(function () {
            $(".GridCustomers").DataTable({
                bLengthChange: true,
                lengthMenu: [[5, 10, -1], [5, 10, "All"]],
                bFilter: true,
                bSort: true,
                bPaginate: true
            });
            $("[id*=lnkEdit]").click(function () {
                $('[id*=admno]').val($(this).closest('tr').find('td').eq(0).html());
                $('[id*=txtName]').val($(this).closest('tr').find('td').eq(1).html());
                $('[id*=txtCountry]').val($(this).closest('tr').find('td').eq(2).html());
                $('#MyPopup').modal('show');
                return false;
            });
        });
    </script>
</asp:Content>
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As New SqlConnection(constr)
            Using cmd As New SqlCommand("SELECT * FROM Customers", con)
                Using sda As New SqlDataAdapter(cmd)
                    cmd.CommandType = CommandType.Text
                    Dim dt As New DataTable()
                    sda.Fill(dt)
                    GridView1.DataSource = dt
                    GridView1.DataBind()
                    GridView1.UseAccessibleHeader = True
                    GridView1.HeaderRow.TableSection = TableRowSection.TableHeader
                End Using
            End Using
        End Using
    End If
End Sub
Protected Sub OnUpdate(ByVal sender As Object, ByVal e As EventArgs)
    ' Code to update the record.
    Dim id As String = Request.Form("txtId")
    Dim name As String = Request.Form("txtName")
    Dim country As String = Request.Form("txtCountry")
    ' Dim category As String = Request.Form("Categoryddl")
    ' Categorym.Text = Request.Form("Categoryddl")
    ' Names.Text = name
    ' Countrys.Text = country
    GridView1.UseAccessibleHeader = True
    GridView1.HeaderRow.TableSection = TableRowSection.TableHeader
End Sub
Screenshot
