Question

Wait, before you start thinking, I would like to clear that I am NOT going to ask the routine differences between Interface and Abstract.

I had gone through the difference between Abstract and Interface in MSDN.

It is said :

By updating the base class, all inheriting classes are automatically updated with the change.
Interfaces, on the other hand, cannot be changed once created. If a new version of
an interface is required, you must create a whole new interface.

See this : –

Can anyone prove this using following example: –

abstract class WashingMachine
{
   abstract public void Wash();
}


class Philips : WashingMachine
{
   public Philips() {  }

   override public void Wash(){//Wash code here....}
}

class Samsung : WashingMachine
{
   public Samsung() {  }

   override public void Wash(){//Wash code here....}
}

class Videocon : WashingMachine
{
   public Videocon() {  }

   override public void Wash(){//Wash code here....}
}

Now, If I added following new abstract method in WashingMachine : –

abstract public void Rinse(int loadSize);

How all inheriting classes (i.e. Philips/Samsung/Videocon) will automatically get updated with the change?

Answer 1

They won’t get updated – you still have to manually add an implementation of Rinse to each and every class that inherits from WashingMachine.

What I believe the MSDN says is that if you have a non-abstract method defined in an abstract class and you change that method, all classes that inherit from the abstract class will benefit from the change automatically.