How To Edit a Programm While It Is running

GentleMen,

I read Somewhere That it is possible to Add Delete Or edit into a programm in real time

While it is running or a programm can write itself but it was not told how

could someone please demostrate asimple example for that. FOr instance

using System;

using Sytem.Reflection;

using ....

namespace EditWhileRunning

{

    public class EditIt

    {

          public int AddTwoNumbers ( int Num1 , Int Num2 )

         {

                     return Num1 + Num2 ;  // could the + sign be changed to - Sign

                                                         // While Running or how can

                                                         // one write a Method       for

                                                          // substration whiel on the fly

         }

 

    }//end class

 

}//end namespace

 

Thankyou

RIGHT_THEN