Inserting dynamic textbox data to database

<legend>Organisation /Company Contacts</legend>
<asp:ScriptManager ID="scrptmgr1" runat="server" />
<asp:UpdatePanel ID="updatepnl1" runat="server" UpdateMode="Conditional">
<triggers>
 <asp:AsyncPostBackTrigger ControlID="btn1" EventName="Click" />
</triggers>
<contenttemplate>
<asp:Table ID="tbl1" runat="server" Height="48px" Width="330px">
 <asp:TableRow ID="tr1" runat="server">
 <asp:TableCell ID="r1_tc1" runat="server">
<asp:Label ID="regdet_llno_lbl" runat="server">Land Line Number:


<asp:TableCell ID="r1_tc2" runat="server" RowSpan="2">
<asp:TextBox ID="regdet_llno_txt" runat="server" />
 <asp:RegularExpressionValidator ID="validator1" runat="server" ControlToValidate="regdet_llno_txt" ErrorMessage="Only numbers are allowed" ValidationExpression="^\d+$">


<asp:TableCell ID="r1_tc3" runat="server">
<asp:Button ID="btn1" runat="server" Text="add" CausesValidation="false" OnClick="btn1_Click" />
 </contenttemplate>

protected void btn1_Click(object sender, EventArgs e)
{
    int a = 3;
    for (; a <= 5; a++)
    {
        TextBox lndline = new TextBox();
        lndline.ID = "lndline_txt" + a;
        r1_tc2.Controls.Add(lndline);
        Literal li1 = new Literal();
        li1.Text = "";
        r1_tc2.Controls.Add(li1);
    }
    int b = 1;
    if (b==1)
    {
        btn1.Enabled = false;
    }
}