how to get textbox value in placeholder on code behind?

Question

I created some textbox and I want to get their value dynamically. Briefly, ı explain my page:

I have dropDown list has number 1 to 15.When the user select number and I

Answer 1

Below code will help you

 protected void ddlUserSelected_SelectedIndexChanged(object sender, EventArgs e)
  {
    for (int a = 1; a <= int.Parse(ddlUserSelected.SelectedItem.Text); a++)
    {

        TextBox txtDate = new TextBox();
        Label lbl = new Label();
        lbl.Text = "
";
        txtDate.Width = 70;
        txtDate.CssClass = "tbl";
        txtDate.ID = "txtDate" + a;
        PlaceHolder1.Controls.Add(txtDate);
        PlaceHolder1.Controls.Add(lbl);

    }
  }
  protected void btnSave_Click(object sender, EventArgs e)
  {

    for (int a = 1; a <= int.Parse(ddlUserSelected.SelectedItem.Text); a++)
    {
        if(Request.Form.Get("txtDate" + a.ToString()) != null)
        {
            var str = Request.Form.Get("txtDate" + a.ToString());
        }        
    }
  }

If you are used master page then use below code

        if (Request.Form.Get("ctl00$ContentPlaceHolder1$txtDate" + a.ToString()) != null)
        {
            var str = Request.Form.Get("ctl00$ContentPlaceHolder1$txtDate" + a.ToString());
        }