How to add or remove Dynamic TextBox and maintain its value on check / uncheck of CheckBoxList using C# in ASP.Net

Hi ashokpumca,

I have created sample code which fullfill your requirement.

HTML

<div>
    <div>
        <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
        <script type="text/javascript">
            $(function () {
                $('[id*=ChkBatchSize]').on('click', function () {
                    if ($(this).is(':checked')) {
                        $('[Id*=hdId]').val($(this).attr('value'));
                    }
                });
            });
        </script>
    </div>
    <asp:HiddenField ID="hdId" runat="server" />
    <asp:Panel ID="phold" runat="server">
    </asp:Panel>
    <table>
        <tr>
            <td style="width: 250px">
                <b>Select Batch Sizes</b>
            </td>
            <td style="width: 412px">
                <asp:CheckBoxList ID="ChkBatchSize" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ChkBatchSize_SelectedIndexChanged"
                    RepeatDirection="Horizontal">
                </asp:CheckBoxList>
            </td>
            <td style="width: 250px">
            </td>
        </tr>
        <tr id="Tr1" runat="server">
            <td style="width: 250px">
                <b>Mother Batch </b>
            </td>
            <td style="width: 412px">
                <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
            </td>
            <td style="width: 250px">
            </td>
        </tr>
    </table>
</div>

C#

private string constring = ConfigurationManager.ConnectionStrings["conString"].ToString();
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        this.GetCustomer();
    }
}

private void GetCustomer()
{
    SqlConnection con = new SqlConnection(constring);
    string strQuery = "SELECT * FROM Customers";
    SqlCommand cmd = new SqlCommand(strQuery, con);
    SqlDataAdapter sda = new SqlDataAdapter(cmd);

    con.Open();
    using (SqlDataReader sdr = cmd.ExecuteReader())
    {
        while (sdr.Read())
        {
            ListItem item = new ListItem();
            item.Text = sdr["Name"].ToString();
            item.Value = sdr["CustomerId"].ToString();
            ChkBatchSize.Items.Add(item);
        }
    }
    con.Close();
    cmd.Dispose();
}

protected void ChkBatchSize_SelectedIndexChanged(object sender, EventArgs e)
{
    foreach (ListItem checkbox in ChkBatchSize.Items)
    {
        if (checkbox.Selected)
        {
            if (checkbox.Value == hdId.Value)
            {
                TextBox tb = new TextBox();
                tb.ID = "txtDynamic" + checkbox.Value;  //Adding checkbox value to Textbox for creating unique textbox ID (e.g. txtDynamic46).
                tb.CssClass = "textnow";
                phold.Controls.Add(tb);
                Literal lt = new Literal();
                lt.Text = "<br/>";
                phold.Controls.Add(lt);
            }
        }
        else
        {
            foreach (Control item in phold.Controls.OfType<Control>())
            {
                if (item.ID == "txtDynamic" + checkbox.Value)
                {
                    phold.Controls.Remove(item);
                }
            }
        }
    }
}

protected void Page_PreInit(object sender, EventArgs e)
{
    List<string> keys = Request.Form.AllKeys.Where(key => key.Contains("txtDynamic")).ToList();
    int i = 1;
    foreach (string key in keys)
    {
        this.CreateTextBox("txtDynamic" + i);
        i++;
    }
}

private void CreateTextBox(string id)
{
    TextBox txt = new TextBox();
    txt.ID = id;
    phold.Controls.Add(txt);
    Literal lt = new Literal();
    lt.Text = "<br />";
    phold.Controls.Add(lt);
}

Screenshot