.NET Scheduled Timer

using System;
using System.Xml;
using System.Xml.XPath;

namespace Schedule
{
	/// <summary>
	/// Local event strorage keeps the last time in memory so that skipped events are not recovered.
	/// </summary>
	public class LocalEventStorage : IEventStorage
	{
		public LocalEventStorage()
		{
			_LastTime = DateTime.MaxValue;
		}

		public void RecordLastTime(DateTime Time)
		{
			_LastTime = Time;
		}

		public DateTime ReadLastTime()
		{
			if (_LastTime == DateTime.MaxValue)
				_LastTime = DateTime.Now;
			return _LastTime;
		}

		DateTime _LastTime;
	}

	/// <summary>
	/// FileEventStorage saves the last time in an XmlDocument so that recovery will include periods that the 
	/// process is shutdown.
	/// </summary>
	public class FileEventStorage : IEventStorage
	{
		public FileEventStorage(string FileName, string XPath)
		{
			_FileName = FileName;
			_XPath = XPath;
		}

		public void RecordLastTime(DateTime Time)
		{
			_Doc.SelectSingleNode(_XPath).Value = Time.ToString();
			_Doc.Save(_FileName);
		}

		public DateTime ReadLastTime()
		{
			_Doc.Load(_FileName);
			string Value = _Doc.SelectSingleNode(_XPath).Value;
			if (Value == null || Value == string.Empty)
				return DateTime.Now;
			return DateTime.Parse(Value);
		}

		string _FileName;
		string _XPath;
		XmlDocument _Doc = new XmlDocument();
	}
}