An Easy to Use Weak Referenced Event Handler Factory for .NET 2.0

// ****************************************************************************
// Copyright Swordfish Computing 2005                                        **
//                                                                           **
// Filename: Swordfish\WeakEventHandlerFactoryTester\SubTotal.cs             **
// Authored by: John Stewien of Swordfish Computing                          **
// Date: September 2005                                                      **
//                                                                           **
// - Change Log -                                                            **
// ****************************************************************************
// $Id: SubTotal.cs,v 1.1 2005/09/28 04:55:46 stewienj Exp $

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

namespace Swordfish.WeakEventHandlerFactoryTester
{
	/// <summary>
	/// Event args for when the value in a SubTotal changes
	/// </summary>
	public class SubTotalDiffArgs : EventArgs
	{
		/// <summary>
		/// The amount that the SubTotal object changed by
		/// </summary>
		public readonly float Diff = 0f;
		
		/// <summary>
		/// Constructor. Intializes class fields.
		/// </summary>
		/// <param name="diff"></param>
		public SubTotalDiffArgs(float diff)
		{
			Diff = diff;
		}
	}

	/// <summary>
	/// Class that just holds a float. Fires and event when
	/// the value of the float gets changed.
	/// </summary>
	public class SubTotal
	{
		/// <summary>
		/// The float value
		/// </summary>
		private float subTotal = 0f;

		/// <summary>
		/// Default Constructor.
		/// </summary>
		public SubTotal()
		{
		}

		/// <summary>
		/// Constructor that initializes the float
		/// </summary>
		/// <param name="value"></param>
		public SubTotal(float value)
		{
			subTotal = value;
		}

		/// <summary>
		/// Allow implicit conversion from a float to make it
		/// easier to create an initialized array of SubTotal objects.
		/// </summary>
		/// <param name="value"></param>
		/// <returns></returns>
		public static implicit operator SubTotal(float value)
		{
			return new SubTotal(value);
		}

		/// <summary>
		/// Gets/Sets the value of the float
		/// </summary>
		public float Value
		{
			get
			{
				return subTotal;
			}
			set
			{
				if (subTotal != value)
				{
					float diff = value-subTotal;
					subTotal = value;
					OnSubTotalChanged(diff);
				}
			}
		}

		/// <summary>
		/// Converts this object to a user readable string
		/// </summary>
		/// <returns></returns>
		public override string ToString()
		{
			return subTotal.ToString();
		}

		/// <summary>
		/// Event for when the float changes value
		/// </summary>
		public event EventHandler<SubTotalDiffArgs> SubTotalChanged;

		/// <summary>
		/// Fires the SubTotalChanged event
		/// </summary>
		/// <param name="diff"></param>
		private void OnSubTotalChanged(float diff)
		{
			if (SubTotalChanged != null)
			{
				SubTotalChanged(this, new SubTotalDiffArgs(diff));

			}
		}
	}
}