C#

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

namespace Dynamic
{
    public partial class DynamicControls : System.Web.UI.Page
    {
        //private property to access the ControlsList in ViewState
        private List<string> ControlsList
        {
            get
            {
                if (ViewState["controls"] == null)
                    ViewState["controls"] = new List<string>();

                return (List<string>)ViewState["controls"];
            }
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            configTextBox.Width = 400;

            if (IsPostBack)
            {
                string config = configTextBox.Text;

                foreach (string labelID in ControlsList)
                {
                    Label label = new Label();
                    label.ID = label.Text = labelID;
                    label.CssClass = "LabelClass";
                    label.Style.Add(HtmlTextWriterStyle.BackgroundColor, "lime");

                    label.Style.Add(HtmlTextWriterStyle.Position, "absolute");
                    label.Style.Add(HtmlTextWriterStyle.Top, getFirstNumber(ref config).ToString() + "px");
                    label.Style.Add(HtmlTextWriterStyle.Left, getFirstNumber(ref config).ToString() + "px");
                    label.Style.Add(HtmlTextWriterStyle.Height, getFirstNumber(ref config).ToString() + "px");
                    label.Style.Add(HtmlTextWriterStyle.Width, getFirstNumber(ref config).ToString() + "px");

                    Container.Controls.Add(label);  // add it to the page
                }
            }
        }

        protected void addLabelButton_Click(object sender, EventArgs e)
        {
            Label label = new Label();
            label.ID = label.Text = "Label" + NextID.ToString();
            label.CssClass = "LabelClass";
            label.Style.Add(HtmlTextWriterStyle.BackgroundColor, "lime");

            Container.Controls.Add(label);  // add it to the page
            ControlsList.Add(label.ID); // save the id
        }

        protected int NextID
        {
            get
            {
                return ControlsList.Count + 1;
            }
        }

        protected int getFirstNumber(ref string line)
        {
            int position = 0;
            int value = 0;

            while (position < line.Length && line[position] != ' ')
                value = 10 * value + line[position++] - '0';

            if (position + 1 < line.Length)
                line = line.Substring(position + 1);

            return value;
        }
    }
}