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

Hi,

I have a dynamic checkboxlist populated from database. I have created textboxes in placeholder when clicked on checkboxlist. But I am unable to pick the value of textboxes.

protected void ChkBatchSize_SelectedIndexChanged(object sender, EventArgs e)
    {
       
        //Check through each of the items
        foreach (ListItem checkbox in ChkBatchSize.Items)
        {
            if (checkbox.Selected)
            {
                TextBox tb = new TextBox();
                tb.ID = "txtDynamic" + checkbox.Value;
                tb.CssClass = "textnow";             
                phold.Controls.Add(tb);
            }
            
        }
    }