AJAX Progress Bar for ASP.NET

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace hmlib.Web.UI.Controls
{
	public partial class Progress
	{
		public string ID { get; private set; }
		private double? _value;
		public double? Value
		{
			get { return this._value; }
			private set
			{
				this._value = value;
				this.ChangedOn = DateTime.Now;
			}
		}
		public DateTime ChangedOn { get; private set; }
		public DateTime CreatedOn { get; private set; }
		private List<string> NewLines = new List<string>();
		private Progress(string id)
		{
			this.ID = id;
			this.Value = null;
			this.ChangedOn = DateTime.Now;
			this.CreatedOn = DateTime.Now;
			Progress._list.Add(this);
			Progress.CleanUp();
		}
		public bool SetProgress(double value)
		{
			this.Value = value;
			return true;
		}
		public bool AddMessageLine(object msg)
		{
			if (msg == null) return false;
			this.NewLines.Add(msg.ToString());
			return true;
		}
		public bool AddMessageLines(string[] lines)
		{
			foreach (var line in lines)
			{
				this.AddMessageLine(line);
			}
			return true;
		}
		public object State { get; set; }
		public void ClearProgress()
		{
			this.Value = null;
			this.NewLines.Clear();
		}
	}
}