Runtime polymorphism/Overriding with example program cod in a c# code

Here's a very simple example:

using System;

class Parent
{
   public virtual void Method(string s)
   {
      Console.WriteLine("Parent.Method called with an argument of {0}", s); 
   }
}

class Child : Parent
{
   public override void Method(string s)
   {
      Console.WriteLine("Child.Method called with an argument of {0}", s); 
   }
}

class Test
{
   static void Main()
   {
       Parent p = new Parent();
       p.Method("Hello"); // Parent's version called because 'p' refers to a Parent object
       p = new Child(); 
       p.Method("Goodbye"); // Child's version is called because 'p' refers to a Child object
       Console.ReadKey();
   }
}

The output is: