Recreate Dynamically Created TextBoxes

Question

User-1385105225 posted

I have a page that will dynamically create text boxes based on a NumberOfFilesValue and place them in a placeholder. This page might postback a few times as the user changes values on the page. I'm not able to find the placeholder in Pre_Init.

using DataServices_v2.Shared;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace DataServices_v2
{
	public partial class test : System.Web.UI.Page
	{
        protected void Page_PreInit(object sender, EventArgs e)
        {
            List<string> keys = Request.Form.AllKeys.Where(key => key.Contains("Filename")).ToList();
            foreach (string key in keys)
            {
                AddTextBoxRow tbRow = new AddTextBoxRow();
                FilenamePlaceholder.Controls.Add(tbRow.NewRow(key));
            }
        }

        protected void Page_Load(object sender, EventArgs e)
		{
            //
		}

        protected void NumberOfFilesValue_TextChanged(object sender, EventArgs e)
        {
            FilenamePlaceholder.Controls.Clear();
            int file_count = Convert.ToInt16(NumberOfFilesValue.Text);
            string pre = "Filename ";
            for (int i = 1; i <= file_count; i++)
            {
                string control_text = pre + i.ToString();
                AddTextBoxRow tbRow = new AddTextBoxRow();
                FilenamePlaceholder.Controls.Add(tbRow.NewRow(control_text));
            }
        }

        protected void BatchSubmit_Click(object sender, EventArgs e)
        {

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using DataServices_v2.Mover;

namespace DataServices_v2.Shared
{
    public class AddTextBoxRow
    {

        public HtmlGenericControl NewRow(string ControlText)
        {
            HtmlGenericControl main_div = new HtmlGenericControl("div"); //main div
            main_div.Attributes["class"] = "form-group";

            Label l = new Label
            {
                ID = ControlText.Replace(" ", String.Empty) + "Label",
                Text = ControlText,
                CssClass = "control-label col-md-2"
            };
            main_div.Controls.Add(l); //add label to main div

            HtmlGenericControl value_div = new HtmlGenericControl("div"); //secondary div
            value_div.Attributes["class"] = "col-md-10";

            TextBox tb = new TextBox
            {
                ID = ControlText.Replace(" ",String.Empty) + "Value",
                CssClass = "form-control"
            };
            value_div.Controls.Add(tb);

            main_div.Controls.Add(value_div); //add secondary div to main div
            return main_div;
        }               
  
    }
}

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="test.aspx.cs" Inherits="DataServices_v2.test" %>
<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">

     <div class="form-group">
            <asp:Label ID="NumberOfFilesLabel" runat="server" Text="Number of Files" CssClass="control-label col-md-2" />
            <div class="col-md-10">
                <asp:TextBox ID="NumberOfFilesValue" runat="server" OnTextChanged="NumberOfFilesValue_TextChanged" AutoPostBack="true" CssClass="form-control" style="width:50px" />
            </div>
        </div>

        <asp:Panel ID="FilenamePlaceholder" runat="server" />
        <hr />
    <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <asp:Button ID="BatchSubmit" runat="server" Text="Create Files" OnClick="BatchSubmit_Click" CssClass="btn btn-default" />
            </div>
        </div>


</asp:Content>

Answer 1

User-1174608757 posted

Hi fr33kyd33ky，

According to your description, I have made a sample here.You couldn't find the placeholder because preInit is fired before the controls are initialized.So, it is obvious that you couldn't get the placeholder. I suggest you to put the control in page_load event. You could see as below:

aspx:

<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">
    <div class="form-group">
            <asp:Label ID="NumberOfFilesLabel" runat="server" Text="Number of Files" CssClass="control-label col-md-2" />
            <div class="col-md-10">
                <asp:TextBox ID="NumberOfFilesValue" runat="server" OnTextChanged="NumberOfFilesValue_TextChanged" AutoPostBack="true" CssClass="form-control" style="width:50px" />
            </div>
        </div>

        <asp:Panel ID="FilenamePlaceholder" runat="server" />
        <hr />
    <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <asp:Button ID="BatchSubmit" runat="server" Text="Create Files" OnClick="BatchSubmit_Click" CssClass="btn btn-default" />
            </div>
        </div>
</asp:Content>

aspx.cs:

public partial class text : System.Web.UI.Page
    {
        protected void Page_PreInit(object sender, EventArgs e)
        {
           
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            List<string> keys = Request.Form.AllKeys.Where(key => key.Contains("Filename")).ToList();
            foreach (string key in keys)
            {
                addrow tbRow = new addrow();

                FilenamePlaceholder.Controls.Add(tbRow.NewRow(key));
            }

        }
        protected void NumberOfFilesValue_TextChanged(object sender, EventArgs e)
        {
            FilenamePlaceholder.Controls.Clear();
            int file_count = Convert.ToInt16(NumberOfFilesValue.Text);
            string pre = "Filename ";
            for (int i = 1; i <= file_count; i++)
            {
                string control_text = pre + i.ToString();
                addrow tbRow = new addrow();
                FilenamePlaceholder.Controls.Add(tbRow.NewRow(control_text));
            }
        }

        protected void BatchSubmit_Click(object sender, EventArgs e)
        {

        }
    }

It shows as below:

Best Regards

Wei Zhang

Answer 2

User-1385105225 posted

Beautiful! Thank you!