Insert Data from ASP.Net GridView to Database using C#

Hi, please help me i want to insert data in the gridview however the data is not inserted into database and the gridview.

Here is my .aspx:

<asp:GridView ID="gvTetapanJenisKenderaan" ClientIDMode="Static" runat="server" AutoGenerateColumns="False" Width="100%"
    CssClass="gridView table table-striped table-bordered" CellPadding="3" Font-Size="Small"
    GridLines="Vertical" ShowFooter="True" ShowHeaderWhenEmpty="True" AllowPaging="True" PageSize="4" OnPageIndexChanging="gvTetapanJenisKenderaan_PageIndexChanging"
    OnRowCommand="gvTetapanJenisKenderaan_RowCommand"
    OnRowEditing="gvTetapanJenisKenderaan_RowEditing"
    OnRowCancelingEdit="gvTetapanJenisKenderaan_RowCancelingEdit"
    OnRowUpdating="gvTetapanJenisKenderaan_RowUpdating"
    OnRowDeleting="gvTetapanJenisKenderaan_RowDeleting" BackColor="White" BorderColor="#999999" BorderStyle="None" BorderWidth="1px">
    <AlternatingRowStyle BackColor="#DCDCDC" />
    <Columns>
        <asp:TemplateField HeaderText="" ItemStyle-HorizontalAlign="Center">
            <ItemTemplate>
                <asp:LinkButton ID="lnkCollapse" runat="server" ToolTip="Collapse" ForeColor="Black" Font-Size="14pt"
                    CommandArgument='<%# Eval("JenamaKenderaanID") %>' OnClick="lnkCollapse_Click"><i class="fa fa-plus"></i>
                </asp:LinkButton>
            </ItemTemplate>
            <ItemStyle HorizontalAlign="Center"></ItemStyle>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Jenis Buatan / Jenama" ItemStyle-HorizontalAlign="Center" HeaderStyle-HorizontalAlign="Center" ItemStyle-Width="60%">
            <HeaderStyle HorizontalAlign="Center"></HeaderStyle>
            <ItemStyle HorizontalAlign="Center" Width="60%"></ItemStyle>
            <ItemTemplate>
                <asp:Label ID="lblJenamaKenderaan" runat="server" Text='<%# Eval("cVehicleMake") %>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="txtJenamaKenderaan" runat="server" Text='<%# Eval("cVehicleMake") %>'></asp:TextBox>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:TextBox ID="txtJenamaKenderaan_Footer" runat="server"></asp:TextBox>
            </FooterTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Tindakan" ItemStyle-HorizontalAlign="Center">
            <ItemTemplate>
                <asp:LinkButton ID="lnkKemaskini" runat="server" ToolTip="Kemaskini" ForeColor="Orange" Font-Size="14pt"
                    CommandArgument='<%# Eval("JenamaKenderaanID") %>' OnClick="lnkKemaskini_Click"><i class="fas fa-marker"></i>
                </asp:LinkButton>
                <asp:LinkButton ID="lnkHapus" runat="server" ToolTip="Hapus" ForeColor="Red" Font-Size="14pt"
                    CommandArgument='<%# Eval("JenamaKenderaanID") %>' OnClick="lnkHapus_Click"><i class="fas fa-trash"></i>
                </asp:LinkButton>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:LinkButton ID="lnkSimpan" runat="server" ToolTip="Simpan" ForeColor="Green" Font-Size="14pt"
                    CommandArgument='<%# Eval("JenamaKenderaanID") %>' OnClick="lnkSimpan_Click"><i class="fa fa-save"></i>
                </asp:LinkButton>
                <asp:LinkButton ID="lnkBatal" runat="server" ToolTip="Batal" ForeColor="Red" Font-Size="14pt"
                    CommandArgument='<%# Eval("JenamaKenderaanID") %>' OnClick="lnkBatal_Click"><i class="fa fa-close"></i>
                </asp:LinkButton>
            </EditItemTemplate>
            <FooterTemplate>
                <asp:LinkButton ID="lnkTambah" runat="server" ToolTip="Tambah" ForeColor="Blue" Font-Size="14pt"
                    CommandArgument='<%# Eval("cVehicleMake") %>' OnClick="lnkTambah_Click"><i class="fa fa-plus-square-o"></i>
                </asp:LinkButton>
            </FooterTemplate>
            <ItemStyle HorizontalAlign="Center"></ItemStyle>
        </asp:TemplateField>
    </Columns>
    <FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
    <HeaderStyle HorizontalAlign="Center" BackColor="#000084" Font-Bold="True" ForeColor="White" />
    <PagerSettings FirstPageText="First" LastPageText="Last" PageButtonCount="4" />
    <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
    <RowStyle BackColor="#EEEEEE" ForeColor="Black" />
    <SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
    <SortedAscendingCellStyle BackColor="#F1F1F1" />
    <SortedAscendingHeaderStyle BackColor="#0000A9" />
    <SortedDescendingCellStyle BackColor="#CAC9C9" />
    <SortedDescendingHeaderStyle BackColor="#000065" />
</asp:GridView>

and behind code :

protected void lnkTambah_Click(object sender, EventArgs e)
{
    foreach (GridViewRow row in gvTetapanJenisKenderaan.Rows)
    {
        TextBox txtJenamaKenderaan = (TextBox)row.FindControl("txtJenamaKenderaan");
        if (txtJenamaKenderaan != null && !string.IsNullOrEmpty(txtJenamaKenderaan.Text))
        {
            using (SqlConnection con = new SqlConnection(conStr))
            {
                con.Open();

                SqlCommand cmd = new SqlCommand("INSERT INTO eLoanVehicleMake (cVehicleMake) VALUES (@cVehicleMake)", con);
                cmd.Parameters.AddWithValue("@cVehicleMake", txtJenamaKenderaan.Text);
                cmd.ExecuteNonQuery();
            }
        }
    }

    GVbind();
}