An Event Pool

using System;
using System.Globalization;

namespace MVCDemo
{
	public delegate void RegisterChangeDelegate(object sender, EventArgs args);

	public class RpnModel : ModelBase
	{
		// 4 register stack
		protected string[] registerStack={"0.00", "0.00", "0.00", "0.00"};
		protected bool newEntryState;
		protected NumberFormatInfo formatProvider;

		public bool NewEntryState
		{
			get {return newEntryState;}
			set
			{
				newEntryState=value;
				eventPool.FireEvent("EntryStateChanged");
			}
		}

		public string X
		{
			get {return registerStack[0];}
			set
			{
				registerStack[0]=value;
				eventPool.FireEvent("X");
			}
		}

		public string Y
		{
			get {return registerStack[1];}
			set
			{
				registerStack[1]=value;
				eventPool.FireEvent("Y");
			}
		}

		public string R3
		{
			get {return registerStack[2];}
			set
			{
				registerStack[2]=value;
				eventPool.FireEvent("R3");
			}
		}

		public string R4
		{
			get {return registerStack[3];}
			set
			{
				registerStack[3]=value;
				eventPool.FireEvent("R4");
			}
		}

		public double DX
		{
			get {return Convert.ToDouble(X);}
			set {X=value.ToString("N", formatProvider);}
		}

		public double DY
		{
			get {return Convert.ToDouble(Y);}
		}

		public RpnModel()
		{
			formatProvider=new NumberFormatInfo();
			formatProvider.NumberDecimalDigits=2;
			newEntryState=true;
			eventPool.Publish("X", "Y", "R3", "R4", "EntryStateChanged");
		}

		public void RollUp()
		{
			string temp=R4;
			R4=R3;
			R3=Y;
			Y=X;
			X=temp;
		}

		public void RollDown()
		{
			string temp=X;
			X=Y;
			Y=R3;
			R3=R4;
			R4=temp;
		}

		public void Push()
		{
			R4=R3;
			R3=Y;
			Y=X;
		}

		public void PopY()
		{
			Y=R3;
			R3=R4;
			R4="0.00";
		}

		public void Exchange()
		{
			string temp=X;
			X=Y;
			Y=temp;
		}

		public void ForceUpdate()
		{
			eventPool.FireAll();
		}

		public void FormatX()
		{
			X=DX.ToString("N", formatProvider);
		}

		public void AddPoint()
		{
			AddCharToX(formatProvider.NumberDecimalSeparator[0]);
		}

		public void AddCharToX(char c)
		{
			if (newEntryState)
			{
				X=c.ToString();
			}
			else
			{
				X+=c;
			}
		}

		public void RemoveCharFromX()
		{
			if (X.Length==1)
			{
				DX=0;
				NewEntryState=true;
			}
			else
			{
				X=X.Substring(0, X.Length-1);
			}
		}

		public void ChangeSign()
		{
			if (DX != 0.00)
			{
				if (X[0] != '-')
				{
					X="-"+X;
				}
				else
				{
					X=X.Substring(1);
				}
			}
		}

		public IMemento GetState()
		{
			IMemento memento=new RpnModelMemento();
			memento.SetState(registerStack);
			return memento;
		}

		public void SetState(IMemento memento)
		{
			((string[])memento.GetState()).CopyTo(registerStack, 0);
			eventPool.FireAll();
		}
	}
}